[SPARK-20092][R][PROJECT INFRA] Add the detection for Scala codes dedicated for R in AppVeyor tests
[SPARK-20092][R][PROJECT INFRA] Add the detection for Scala codes dedicated for R in AppVeyor tests

## What changes were proposed in this pull request?

We are currently detecting the changes in `R/` directory only and then trigger AppVeyor tests.

It seems we need to tests when there are Scala codes dedicated for R in `core/src/main/scala/org/apache/spark/api/r/`, `sql/core/src/main/scala/org/apache/spark/sql/api/r/` and `mllib/src/main/scala/org/apache/spark/ml/r/` too.

This will enables the tests, for example, for SPARK-20088.

## How was this patch tested?

Tests with manually created PRs.

- Changes in `sql/core/src/main/scala/org/apache/spark/sql/api/r/SQLUtils.scala` https://github.com/spark-test/spark/pull/13
- Changes in `core/src/main/scala/org/apache/spark/api/r/SerDe.scala` https://github.com/spark-test/spark/pull/12
- Changes in `README.md` https://github.com/spark-test/spark/pull/14

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #17427 from HyukjinKwon/SPARK-20092.

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