[SPARK-19270][FOLLOW-UP][ML] PySpark GLR model.summary should return a printable representation.
[SPARK-19270][FOLLOW-UP][ML] PySpark GLR model.summary should return a printable representation.

## What changes were proposed in this pull request?
PySpark GLR ```model.summary``` should return a printable representation by calling Scala ```toString```.

## How was this patch tested?
```
from pyspark.ml.regression import GeneralizedLinearRegression
dataset = spark.read.format("libsvm").load("data/mllib/sample_linear_regression_data.txt")
glr = GeneralizedLinearRegression(family="gaussian", link="identity", maxIter=10, regParam=0.3)
model = glr.fit(dataset)
model.summary
```
Before this PR:
![image](https://user-images.githubusercontent.com/1962026/29021059-e221633e-7b96-11e7-8d77-5d53f89c81a9.png)
After this PR:
![image](https://user-images.githubusercontent.com/1962026/29021097-fce80fa6-7b96-11e7-8ab4-7e113d447d5d.png)

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #18870 from yanboliang/spark-19270.

dbtsai/spark,mike0sv/spark,WindCanDie/spark,caneGuy/spark,dbtsai/spark,zuotingbing/spark,yanboliang/spark,maropu/spark,LantaoJin/spark,icexelloss/spark,zuotingbing/spark,ioana-delaney/spark,highfei2011/spark,akopich/spark,milliman/spark,markhamstra/spark,sahilTakiar/spark,witgo/spark,xuanyuanking/spark,goldmedal/spark,sureshthalamati/spark,SHASHANKB/spark,adrian-ionescu/apache-spark,guoxiaolongzte/spark,shubhamchopra/spark,gengliangwang/spark,ericvandenbergfb/spark,eyalfa/spark,SHASHANKB/spark,witgo/spark,HyukjinKwon/spark,stanzhai/spark,ConeyLiu/spark,jiangxb1987/spark,lxsmnv/spark,apache/spark,jiangxb1987/spark,jkbradley/spark,bravo-zhang/spark,darionyaphet/spark,brad-kaiser/spark,holdenk/spark,joseph-torres/spark,ueshin/apache-spark,akopich/spark,wzhfy/spark,zzcclp/spark,wangyum/spark,hhbyyh/spark,hvanhovell/spark,apache/spark,saltstar/spark,holdenk/spark,mdespriee/spark,guoxiaolongzte/spark,shubhamchopra/spark,apache/spark,jkbradley/spark,wangyum/spark,shaneknapp/spark,nchammas/spark,1haodian/spark,xuanyuanking/spark,byakuinss/spark,nlalevee/spark,holdenk/spark,guoxiaolongzte/spark,ericvandenbergfb/spark,facaiy/spark,JoshRosen/spark,witgo/spark,eyalfa/spark,ahnqirage/spark,JoshRosen/spark,ericvandenbergfb/spark,stanzhai/spark,saltstar/spark,tejasapatil/spark,BryanCutler/spark,nchammas/spark,apache/spark,srowen/spark,bravo-zhang/spark,rekhajoshm/spark,spark-test/spark,techaddict/spark,esi-mineset/spark,spark-test/spark,bravo-zhang/spark,byakuinss/spark,highfei2011/spark,ddna1021/spark,ron8hu/spark,ajaysaini725/spark,actuaryzhang/spark,rezasafi/spark,lxsmnv/spark,nlalevee/spark,facaiy/spark,ajaysaini725/spark,SHASHANKB/spark,goldmedal/spark,xflin/spark,bdrillard/spark,mike0sv/spark,pgandhi999/spark,xflin/spark,shuangshuangwang/spark,zhouyejoe/spark,wangmiao1981/spark,someorz/spark,mike0sv/spark,techaddict/spark,guoxiaolongzte/spark,sureshthalamati/spark,highfei2011/spark,shubhamchopra/spark,shaneknapp/spark,BryanCutler/spark,maropu/spark,kiszk/spark,gengliangwang/spark,kevinyu98/spark,zero323/spark,taroplus/spark,dbtsai/spark,aosagie/spark,bdrillard/spark,zzcclp/spark,adrian-ionescu/apache-spark,matthewfranglen/spark,caneGuy/spark,highfei2011/spark,ConeyLiu/spark,bdrillard/spark,sahilTakiar/spark,narahari92/spark,darionyaphet/spark,chuckchen/spark,cloud-fan/spark,michalsenkyr/spark,actuaryzhang/spark,ptkool/spark,xflin/spark,WindCanDie/spark,UndeadBaneGitHub/spark,WindCanDie/spark,akopich/spark,ron8hu/spark,tejasapatil/spark,ConeyLiu/spark,apache/spark,icexelloss/spark,goldmedal/spark,markhamstra/spark,mahak/spark,alunarbeach/spark,1haodian/spark,ioana-delaney/spark,cin/spark,nlalevee/spark,minixalpha/spark,jiangxb1987/spark,narahari92/spark,HyukjinKwon/spark,sahilTakiar/spark,minixalpha/spark,dongjoon-hyun/spark,milliman/spark,zhouyejoe/spark,BryanCutler/spark,gengliangwang/spark,rednaxelafx/apache-spark,vinodkc/spark,guoxiaolongzte/spark,lvdongr/spark,ericvandenbergfb/spark,cloud-fan/spark,xflin/spark,zero323/spark,icexelloss/spark,chuckchen/spark,rikima/spark,taroplus/spark,tejasapatil/spark,ueshin/apache-spark,nlalevee/spark,nlalevee/spark,BryanCutler/spark,spark-test/spark,ueshin/apache-spark,eyalfa/spark,ptkool/spark,someorz/spark,pgandhi999/spark,UndeadBaneGitHub/spark,dongjoon-hyun/spark,taroplus/spark,SHASHANKB/spark,mike0sv/spark,adrian-ionescu/apache-spark,spark-test/spark,ddna1021/spark,ajaysaini725/spark,maropu/spark,caneGuy/spark,jiangxb1987/spark,esi-mineset/spark,spark-test/spark,skonto/spark,narahari92/spark,tengpeng/spark,joseph-torres/spark,UndeadBaneGitHub/spark,markhamstra/spark,jkbradley/spark,hvanhovell/spark,ptkool/spark,xuanyuanking/spark,gengliangwang/spark,Aegeaner/spark,maropu/spark,kevinyu98/spark,SHASHANKB/spark,janewangfb/spark,apache/spark,cin/spark,aray/spark,vinodkc/spark,szhem/spark,dbtsai/spark,WeichenXu123/spark,highfei2011/spark,shubhamchopra/spark,guoxiaolongzte/spark,holdenk/spark,nchammas/spark,apache/spark,vinodkc/spark,narahari92/spark,aray/spark,srowen/spark,rezasafi/spark,icexelloss/spark,shuangshuangwang/spark,byakuinss/spark,ron8hu/spark,ahnqirage/spark,pgandhi999/spark,hhbyyh/spark,HyukjinKwon/spark,xflin/spark,rednaxelafx/apache-spark,WeichenXu123/spark,caneGuy/spark,minixalpha/spark,goldmedal/spark,aray/spark,rekhajoshm/spark,ddna1021/spark,wzhfy/spark,maropu/spark,UndeadBaneGitHub/spark,shaneknapp/spark,chuckchen/spark,wangmiao1981/spark,debugger87/spark,tengpeng/spark,facaiy/spark,techaddict/spark,saltstar/spark,rekhajoshm/spark,darionyaphet/spark,mahak/spark,rednaxelafx/apache-spark,HyukjinKwon/spark,zero323/spark,WeichenXu123/spark,szhem/spark,ahnqirage/spark,WindCanDie/spark,UndeadBaneGitHub/spark,spark-test/spark,szhem/spark,rezasafi/spark,xuanyuanking/spark,kevinyu98/spark,techaddict/spark,rikima/spark,zero323/spark,LantaoJin/spark,LantaoJin/spark,zhouyejoe/spark,taroplus/spark,eyalfa/spark,chuckchen/spark,bdrillard/spark,cloud-fan/spark,sureshthalamati/spark,xflin/spark,vinodkc/spark,nchammas/spark,hhbyyh/spark,dongjoon-hyun/spark,1haodian/spark,saltstar/spark,LantaoJin/spark,alunarbeach/spark,ajaysaini725/spark,witgo/spark,byakuinss/spark,byakuinss/spark,ericvandenbergfb/spark,wangyum/spark,adrian-ionescu/apache-spark,ConeyLiu/spark,alunarbeach/spark,WeichenXu123/spark,kevinyu98/spark,rednaxelafx/apache-spark,techaddict/spark,maropu/spark,hvanhovell/spark,chuckchen/spark,SHASHANKB/spark,wangmiao1981/spark,adrian-ionescu/apache-spark,byakuinss/spark,ptkool/spark,bravo-zhang/spark,ericvandenbergfb/spark,stanzhai/spark,cin/spark,zuotingbing/spark,szhem/spark,dongjoon-hyun/spark,tejasapatil/spark,holdenk/spark,zuotingbing/spark,narahari92/spark,kiszk/spark,skonto/spark,michalsenkyr/spark,JoshRosen/spark,stanzhai/spark,wangyum/spark,hvanhovell/spark,aosagie/spark,minixalpha/spark,zuotingbing/spark,pgandhi999/spark,ddna1021/spark,szhem/spark,shaneknapp/spark,milliman/spark,JoshRosen/spark,shuangshuangwang/spark,janewangfb/spark,guoxiaolongzte/spark,Aegeaner/spark,ajaysaini725/spark,jiangxb1987/spark,debugger87/spark,brad-kaiser/spark,caneGuy/spark,goldmedal/spark,taroplus/spark,icexelloss/spark,1haodian/spark,Aegeaner/spark,ajaysaini725/spark,nchammas/spark,ueshin/apache-spark,WindCanDie/spark,ahnqirage/spark,jkbradley/spark,actuaryzhang/spark,shaneknapp/spark,ioana-delaney/spark,sureshthalamati/spark,tengpeng/spark,facaiy/spark,mdespriee/spark,witgo/spark,zuotingbing/spark,akopich/spark,bravo-zhang/spark,saltstar/spark,hhbyyh/spark,bravo-zhang/spark,ericvandenbergfb/spark,mdespriee/spark,ddna1021/spark,aray/spark,jkbradley/spark,srowen/spark,gengliangwang/spark,eyalfa/spark,shubhamchopra/spark,jiangxb1987/spark,narahari92/spark,milliman/spark,rednaxelafx/apache-spark,wzhfy/spark,akopich/spark,zzcclp/spark,mdespriee/spark,shuangshuangwang/spark,ptkool/spark,1haodian/spark,mahak/spark,janewangfb/spark,eyalfa/spark,aray/spark,minixalpha/spark,debugger87/spark,mahak/spark,hvanhovell/spark,BryanCutler/spark,saltstar/spark,janewangfb/spark,wangyum/spark,BryanCutler/spark,aosagie/spark,lvdongr/spark,wangmiao1981/spark,Aegeaner/spark,kiszk/spark,brad-kaiser/spark,kiszk/spark,yanboliang/spark,dbtsai/spark,shuangshuangwang/spark,lxsmnv/spark,debugger87/spark,esi-mineset/spark,stanzhai/spark,rednaxelafx/apache-spark,rekhajoshm/spark,zhouyejoe/spark,wangmiao1981/spark,lvdongr/spark,kevinyu98/spark,JoshRosen/spark,nlalevee/spark,darionyaphet/spark,rekhajoshm/spark,LantaoJin/spark,tengpeng/spark,adrian-ionescu/apache-spark,pgandhi999/spark,LantaoJin/spark,WeichenXu123/spark,zzcclp/spark,kiszk/spark,xuanyuanking/spark,UndeadBaneGitHub/spark,shubhamchopra/spark,ueshin/apache-spark,gengliangwang/spark,zuotingbing/spark,markhamstra/spark,alunarbeach/spark,kevinyu98/spark,narahari92/spark,ConeyLiu/spark,michalsenkyr/spark,actuaryzhang/spark,michalsenkyr/spark,sahilTakiar/spark,zhouyejoe/spark,icexelloss/spark,mahak/spark,yanboliang/spark,tejasapatil/spark,dbtsai/spark,goldmedal/spark,rednaxelafx/apache-spark,akopich/spark,ahnqirage/spark,nchammas/spark,BryanCutler/spark,alunarbeach/spark,sureshthalamati/spark,chuckchen/spark,zzcclp/spark,vinodkc/spark,mahak/spark,aray/spark,yanboliang/spark,nlalevee/spark,ahnqirage/spark,brad-kaiser/spark,ueshin/apache-spark,rekhajoshm/spark,rekhajoshm/spark,zero323/spark,shubhamchopra/spark,kiszk/spark,michalsenkyr/spark,lxsmnv/spark,maropu/spark,zzcclp/spark,spark-test/spark,yanboliang/spark,debugger87/spark,someorz/spark,JoshRosen/spark,ajaysaini725/spark,wangyum/spark,zhouyejoe/spark,pgandhi999/spark,stanzhai/spark,nchammas/spark,tejasapatil/spark,zhouyejoe/spark,srowen/spark,xuanyuanking/spark,joseph-torres/spark,xuanyuanking/spark,mahak/spark,wangmiao1981/spark,dongjoon-hyun/spark,WeichenXu123/spark,michalsenkyr/spark,joseph-torres/spark,tejasapatil/spark,Aegeaner/spark,facaiy/spark,rezasafi/spark,darionyaphet/spark,wzhfy/spark,sureshthalamati/spark,adrian-ionescu/apache-spark,ioana-delaney/spark,srowen/spark,srowen/spark,WeichenXu123/spark,aosagie/spark,markhamstra/spark,lxsmnv/spark,actuaryzhang/spark,lxsmnv/spark,ueshin/apache-spark,sahilTakiar/spark,debugger87/spark,cin/spark,Aegeaner/spark,skonto/spark,rikima/spark,minixalpha/spark,bdrillard/spark,taroplus/spark,debugger87/spark,ConeyLiu/spark,someorz/spark,facaiy/spark,yanboliang/spark,milliman/spark,dbtsai/spark,ddna1021/spark,lvdongr/spark,aosagie/spark,dongjoon-hyun/spark,UndeadBaneGitHub/spark,techaddict/spark,WindCanDie/spark,wzhfy/spark,darionyaphet/spark,lxsmnv/spark,holdenk/spark,cin/spark,aosagie/spark,sureshthalamati/spark,esi-mineset/spark,ptkool/spark,cin/spark,jkbradley/spark,sahilTakiar/spark,wzhfy/spark,brad-kaiser/spark,hhbyyh/spark,zero323/spark,caneGuy/spark,tengpeng/spark,HyukjinKwon/spark,stanzhai/spark,ahnqirage/spark,LantaoJin/spark,joseph-torres/spark,ddna1021/spark,mike0sv/spark,lvdongr/spark,hvanhovell/spark,esi-mineset/spark,cloud-fan/spark,srowen/spark,jkbradley/spark,ptkool/spark,hhbyyh/spark,aosagie/spark,michalsenkyr/spark,byakuinss/spark,vinodkc/spark,xflin/spark,lvdongr/spark,cin/spark,highfei2011/spark,highfei2011/spark,actuaryzhang/spark,millim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