[SPARK-6591] [SQL] Python data source load options should auto convert common types into strings
[SPARK-6591] [SQL] Python data source load options should auto convert common types into strings

JIRA: https://issues.apache.org/jira/browse/SPARK-6591

Author: Yijie Shen <henry.yijieshen@gmail.com>

Closes #7926 from yjshen/py_dsload_opt and squashes the following commits:

b207832 [Yijie Shen] fix style
efdf834 [Yijie Shen] resolve comment
7a8f6a2 [Yijie Shen] lowercase
822e769 [Yijie Shen] convert load opts to string

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