[SPARK-6275][Documentation]Miss toDF() function in docs/sql-programming-guide.md
[SPARK-6275][Documentation]Miss toDF() function in docs/sql-programming-guide.md

Miss `toDF()` function in docs/sql-programming-guide.md

Author: zzcclp <xm_zzc@sina.com>

Closes #4977 from zzcclp/SPARK-6275 and squashes the following commits:

9a96c7b [zzcclp] Miss toDF()

apache/spark,BryanCutler/spark,metamx/spark,szhem/spark,jiangxb1987/spark,icexelloss/spark,dbtsai/spark,rednaxelafx/apache-spark,rednaxelafx/apache-spark,maropu/spark,hhbyyh/spark,aosagie/spark,pronix/spark,aokolnychyi/spark,vinodkc/spark,shubhamchopra/spark,hvanhovell/spark,stanzhai/spark,shuangshuangwang/spark,SnappyDataInc/spark,1haodian/spark,Aegeaner/spark,ddna1021/spark,shubhamchopra/spark,facaiy/spark,metamx/spark,rikima/spark,mahak/spark,gioenn/xSpark,wangyum/spark,publicRoman/spark,WindCanDie/spark,nlalevee/spark,actuaryzhang/spark,apache-spark-on-k8s/spark,ericvandenbergfb/spark,xflin/spark,brad-kaiser/spark,byakuinss/spark,zhouyejoe/spark,ueshin/apache-spark,jkbradley/spark,aosagie/spark,rezasafi/spark,HyukjinKwon/spark,shubhamchopra/spark,michalsenkyr/spark,liutang123/spark,caneGuy/spark,aray/spark,liutang123/spark,MLnick/spark,panfengfeng/spark,BryanCutler/spark,rezasafi/spark,shubhamchopra/spark,witgo/spark,chuckchen/spark,jianran/spark,mahak/spark,ueshin/apache-spark,UndeadBaneGitHub/spark,highfei2011/spark,gioenn/xSpark,wangmiao1981/spark,ibm-research-ireland/sparkoscope,matthewfranglen/spark,HyukjinKwon/spark,stanzhai/spark,someorz/spark,zuotingbing/spark,narahari92/spark,huang1900/spark,minixalpha/spark,kiszk/spark,ioana-delaney/spark,saturday-shi/spark,minixalpha/spark,ajaysaini725/spark,loneknightpy/spark,sureshthalamati/spark,szhem/spark,esi-mineset/spark,chuckchen/spark,icexelloss/spark,nchammas/spark,ioana-delaney/spark,esi-mineset/spark,pgandhi999/spark,patrick-nicholson/spark,techaddict/spark,zuotingbing/spark,byakuinss/spark,wangmiao1981/spark,apache/spark,big-pegasus/spark,techaddict/spark,dhruve/spark,highfei2011/spark,ddna1021/spark,sachintyagi22/spark,highfei2011/spark,sahilTakiar/spark,ericvandenbergfb/spark,lvdongr/spark,setjet/spark,setjet/spark,yanboliang/spark,liyichao/spark,dongjoon-hyun/spark,dhruve/spark,kiszk/spark,rekhajoshm/spark,zuotingbing/spark,skonto/spark,JoshRosen/spark,WindCanDie/spark,saturday-shi/spark,rikima/spark,maropu/spark,andrewor14/iolap,andrewor14/spark,ron8hu/spark,techaddict/spark,wangmiao1981/spark,metamx/spark,adrian-ionescu/apache-spark,guoxiaolongzte/spark,cin/spark,markhamstra/spark,eyalfa/spark,tejasapatil/spark,mdespriee/spark,shaneknapp/spark,poffuomo/spark,debugger87/spark,jrshust/spark,lvdongr/spark,mzl9039/spark,patrick-nicholson/spark,rekhajoshm/spark,map222/spark,michalsenkyr/spark,taroplus/spark,andrewor14/iolap,minixalpha/spark,JoshRosen/spark,rekhajoshm/spark,ron8hu/spark,wangyum/spark,rikima/spark,map222/spark,setjet/spark,LantaoJin/spark,MLnick/spark,aokolnychyi/spark,zzcclp/spark,zero323/spark,lxsmnv/spark,dbtsai/spark,BryanCutler/spark,metamx/spark,patrick-nicholson/spark,dongjoon-hyun/spark,bOOm-X/spark,kevinyu98/spark,xuanyuanking/spark,JoshRosen/spark,HyukjinKwon/spark,someorz/spark,sureshthalamati/spark,maropu/spark,ahnqirage/spark,brad-kaiser/spark,sureshthalamati/spark,jiangxb1987/spark,jlopezmalla/spark,nilsgrabbert/spark,metamx/spark,ueshin/apache-spark,zero323/spark,1haodian/spark,WeichenXu123/spark,janewangfb/spark,zero323/spark,pgandhi999/spark,witgo/spark,gengliangwang/spark,ueshin/apache-spark,BryanCutler/spark,ibm-research-ireland/sparkoscope,1haodian/spark,caneGuy/spark,apache-spark-on-k8s/spark,WindCanDie/spark,taroplus/spark,markhamstra/spark,skonto/spark,nilsgrabbert/spark,apache/spark,minixalpha/spark,ibm-research-ireland/sparkoscope,JoshRosen/spark,sachintyagi22/spark,techaddict/spark,facaiy/spark,aray/spark,spark-test/spark,joseph-torres/spark,srowen/spark,highfei2011/spark,rikima/spark,mike0sv/spark,aray/spark,rednaxelafx/apache-spark,debugger87/spark,ddna1021/spark,akopich/spark,stanzhai/spark,zzcclp/spark,caneGuy/spark,skonto/spark,kevinyu98/spark,hhbyyh/spark,eyalfa/spark,apache/spark,nlalevee/spark,ahnqirage/spark,zuotingbing/spark,ConeyLiu/spark,esi-mineset/spark,milliman/spark,SHASHANKB/spark,janewangfb/spark,vinodkc/spark,xuanyuanking/spark,shuangshuangwang/spark,adrian-ionescu/apache-spark,eyalfa/spark,cin/spark,chuckchen/spark,mahak/spark,aray/spark,joseph-torres/spark,BryanCutler/spark,hvanhovell/spark,vinodkc/spark,darionyaphet/spark,big-pegasus/spark,darionyaphet/spark,kiszk/spark,minixalpha/spark,jkbradley/spark,ajaysaini725/spark,Aegeaner/spark,bdrillard/spark,rednaxelafx/apache-spark,SnappyDataInc/spark,holdenk/spark,poffuomo/spark,spark-test/spark,wangyum/spark,MLnick/spark,facaiy/spark,brad-kaiser/spark,lxsmnv/spark,kiszk/spark,srowen/spark,spark-test/spark,patrick-nicholson/spark,michalsenkyr/spark,nilsgrabbert/spark,holdenk/spark,apache/spark,big-pegasus/spark,cloud-fan/spark,spark-test/spark,lxsmnv/spark,nchammas/spark,1haodian/spark,poffuomo/spark,byakuinss/spark,poffuomo/spark,cloud-fan/spark,mike0sv/spark,shuangshuangwang/spark,debugger87/spark,HyukjinKwon/spark,esi-mineset/spark,markhamstra/spark,jkbradley/spark,saltstar/spark,pronix/spark,SHASHANKB/spark,bdrillard/spark,sahilTakiar/spark,haowu80s/spark,ddna1021/spark,kimoonkim/spark,jrshust/spark,aosagie/spark,andrewor14/spark,mahak/spark,JoshRosen/spark,szhem/spark,Aegeaner/spark,hvanhovell/spark,jianran/spark,map222/spark,tengpeng/spark,saltstar/spark,goldmedal/spark,wzhfy/spark,chuckchen/spark,adrian-ionescu/apache-spark,rednaxelafx/apache-spark,jkbradley/spark,apache-spark-on-k8s/spark,stanzhai/spark,JoshRosen/spark,rezasafi/spark,metamx/spark,dbtsai/spark,loneknightpy/spark,saturday-shi/spark,janewangfb/spark,haowu80s/spark,publicRoman/spark,huang1900/spark,wzhfy/spark,ron8hu/spark,ueshin/apache-spark,LantaoJin/spark,skonto/spark,LantaoJin/spark,rikima/spark,holdenk/spark,srowen/spark,cin/spark,andrewor14/iolap,big-pegasus/spark,dhruve/spark,andrewor14/spark,andrewor14/iolap,sachintyagi22/spark,debugger87/spark,spark-test/spark,kimoonkim/spark,yanboliang/spark,xflin/spark,bravo-zhang/spark,hvanhovell/spark,nchammas/spark,JerryLead/spark,srowen/spark,kimoonkim/spark,sureshthalamati/spark,bravo-zhang/spark,michalsenkyr/spark,darionyaphet/spark,rezasafi/spark,LantaoJin/spark,mahak/spark,zzcclp/spark,jrshust/spark,esi-mineset/spark,wangyum/spark,jkbradley/spark,michalsenkyr/spark,mahak/spark,ahnqirage/spark,ahnqirage/spark,saturday-shi/spark,saltstar/spark,HyukjinKwon/spark,darionyaphet/spark,guoxiaolongzte/spark,ioana-delaney/spark,zhouyejoe/spark,gioenn/xSpark,wzhfy/spark,jiangxb1987/spark,rikima/spark,WeichenXu123/spark,jiangxb1987/spark,bravo-zhang/spark,Panos-Bletsos/spark-cost-model-optimizer,milliman/spark,shaneknapp/spark,hhbyyh/spark,ioana-delaney/spark,MLnick/spark,nchammas/spark,bravo-zhang/spark,lvdongr/spark,ConeyLiu/spark,mdespriee/spark,janewangfb/spark,zuotingbing/spark,MLnick/spark,ConeyLiu/spark,markhamstra/spark,haowu80s/spark,bOOm-X/spark,ron8hu/spark,map222/spark,sachintyagi22/spark,andrewor14/iolap,Panos-Bletsos/spark-cost-model-optimizer,cin/spark,eyalfa/spark,brad-kaiser/spark,jlopezmalla/spark,shuangshuangwang/spark,BryanCutler/spark,xflin/spark,apache/spark,SHASHANKB/spark,pronix/spark,actuaryzhang/spark,akopich/spark,srowen/spark,UndeadBaneGitHub/spark,taroplus/spark,caneGuy/spark,rednaxelafx/apache-spark,kiszk/spark,zero323/spark,pronix/spark,srowen/spark,narahari92/spark,mzl9039/spark,hhbyyh/spark,pgandhi999/spark,aokolnychyi/spark,zuotingbing/spark,rednaxelafx/apache-spark,ddna1021/spark,ibm-research-ireland/sparkoscope,zzcclp/spark,lvdongr/spark,goldmedal/spark,SHASHANKB/spark,ioana-delaney/spark,caneGuy/spark,brad-kaiser/spark,jianran/spark,tengpeng/spark,aosagie/spark,xuanyuanking/spark,yanboliang/spark,holdenk/spark,witgo/spark,dbtsai/spark,akopich/spark,shubhamchopra/spark,joseph-torres/spark,rekhajoshm/spark,ericvandenbergfb/spark,akopich/spark,panfengfeng/spark,tengpeng/spark,darionyaphet/spark,maropu/spark,SHASHANKB/spark,alunarbeach/spark,shuangshuangwang/spark,setjet/spark,dhruve/spark,spark-test/spark,zhouyejoe/spark,witgo/spark,cloud-fan/spark,kiszk/spark,panfengfeng/spark,kiszk/spark,jrshust/spark,lxsmnv/spark,SnappyDataInc/spark,shaneknapp/spark,zero323/spark,cloud-fan/spark,kissmetrics/spark,actuaryzhang/spark,pgandhi999/spark,vinodkc/spark,mike0sv/spark,yanboliang/spark,wangmiao1981/spark,mdespriee/spark,rekhajoshm/spark,ron8hu/spark,icexelloss/spark,hhbyyh/spark,szhem/spark,stanzhai/spark,sureshthalamati/spark,michalsenkyr/spark,markhamstra/spark,holdenk/spark,jlopezmalla/spark,janewangfb/spark,JoshRosen/spark,setjet/spark,actuaryzhang/spark,ConeyLiu/spark,publicRoman/spark,publicRoman/spark,icexelloss/spark,mdespriee/spark,milliman/spark,markhamstra/spark,JerryLead/spark,eyalfa/spark,byakuinss/spark,skonto/spark,ericvandenbergfb/spark,yanboliang/spark,wzhfy/spark,dongjoon-hyun/spark,xuanyuanking/spark,big-pegasus/spark,kevinyu98/spark,ConeyLiu/spark,dbtsai/spark,saturday-shi/spark,wzhfy/spark,saltstar/spark,stanzhai/spark,1haodian/spark,aosagie/spark,rekhajoshm/spark,icexelloss/spark,yanboliang/spark,1haodian/spark,haowu80s/spark,lxsmnv/spark,markhamstra/spark,publicRoman/spark,shuangshuangwang/spark,map222/spark,darionyaphet/spark,bOOm-X/spark,saltstar/spark,nlalevee/spark,kissmetrics/spark,SnappyDataInc/spark,loneknightpy/spark,tejasapatil/spark,caneGuy/spark,someorz/spark,andrewor14/spark,gengliangwang/spark,zzcclp/spark,eyalfa/spark,cin/spark,dhruve/spark,dongjoon-hyun/spark,rezasafi/spark,adrian-ionescu/apache-spark,highfei2011/spark,dhruve/spark,szhem/spark,kissmetrics/spark,jkbradley/spark,rekhajoshm/spark,Panos-Bletsos/spark-cost-model-optimizer,poffuomo/spark,facaiy/spark,SnappyDataInc/spark,mzl9039/spark,gioenn/xSpark,ajaysaini725/spark,aosagie/spark,liyichao/spark,jiangxb1987/spark,esi-mineset/spark,haowu80s/spark,SnappyDataInc/spark,aray/spark,ajaysaini725/spark,janewangfb/spark,akopich/spark,narahari92/spark,mike0sv/spark,bdrillard/spark,skonto/spark,goldmedal/spark,shaneknapp/spark,dongjoon-hyun/spark,adrian-ionescu/apache-spark,minixalpha/spark,rezasafi/spark,bdrillard/spark,mzl9039/spark,huang1900/spark,lxsmnv/spark,pgandhi999/spark,andrewor14/spark,taroplus/spark,ptkool/spark,lvdongr/spark,esi-mineset/spark,mzl9039/spark,alunarbeach/spark,joseph-torres/spark,ptkool/spar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,cin/spark,tengpeng/spark,panfengfeng/spark,mike0sv/spark,someorz/spark,ajaysaini725/spark,apache/spark,techaddict/spark,alunarbeach/spark,lvdongr/spark,kimoonkim/spark,bOOm-X/spark,xuanyuanking/spark,someorz/spark,bravo-zhang/spark,tejasapatil/spark,patrick-nicholson/spark,byakuinss/spark,guoxiaolongzte/spark,milliman/spark,ron8hu/spark,HyukjinKwon/spark,andrewor14/iolap,kevinyu98/spark,ddna1021/spark,mdespriee/spark,aokolnychyi/spark,ptkool/spark,dbtsai/spark,kissmetrics/spark,panfengfeng/spark,chuckchen/spark,WeichenXu123/spark,kevinyu98/spark,kissmetrics/spark,vinodkc/spark,maropu/spark,adrian-ionescu/apache-spark,dongjoon-hyun/spark,saltstar/spark,ahnqirage/spark,yanboliang/spark,wangyum/spark,jlopezmalla/spark,xflin/spark,sachintyagi22/spark,Aegeaner/spark,witgo/spark,zuotingbing/spark,actuaryzhang/spark,ptkool/spark,gioenn/xSpark