create gpdb_pr pipeline
create gpdb_pr pipeline

When PRs are submitted, trigger a build and then run ICG tests. 
Its output will be placed in separate folder from other pipelines.

Signed-off-by: Gang Xiong <5614de4ed36375d47b39bf47c8bdae2cb0cd0d22@pivotal.io>
Chibin/gpdb,50wu/gpdb,jmcatamney/gpdb,rvs/gpdb,Chibin/gpdb,Quikling/gpdb,xinzweb/gpdb,xinzweb/gpdb,lisakowen/gpdb,jmcatamney/gpdb,lintzc/gpdb,yuanzhao/gpdb,rvs/gpdb,lisakowen/gpdb,janebeckman/gpdb,yuanzhao/gpdb,adam8157/gpdb,ashwinstar/gpdb,50wu/gpdb,edespino/gpdb,rvs/gpdb,lisakowen/gpdb,janebeckman/gpdb,rvs/gpdb,greenplum-db/gpdb,Chibin/gpdb,rvs/gpdb,lisakowen/gpdb,Quikling/gpdb,ashwinstar/gpdb,Quikling/gpdb,yuanzhao/gpdb,edespino/gpdb,janebeckman/gpdb,janebeckman/gpdb,jmcatamney/gpdb,xinzweb/gpdb,kaknikhil/gpdb,ashwinstar/gpdb,adam8157/gpdb,Chibin/gpdb,adam8157/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,Quikling/gpdb,lisakowen/gpdb,adam8157/gpdb,janebeckman/gpdb,xinzweb/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,Chibin/gpdb,yuanzhao/gpdb,greenplum-db/gpdb,edespino/gpdb,50wu/gpdb,lintzc/gpdb,kaknikhil/gpdb,50wu/gpdb,Quikling/gpdb,janebeckman/gpdb,lintzc/gpdb,Quikling/gpdb,cjcjameson/gpdb,kaknikhil/gpdb,ashwinstar/gpdb,adam8157/gpdb,lisakowen/gpdb,janebeckman/gpdb,lintzc/gpdb,Quikling/gpdb,rvs/gpdb,edespino/gpdb,adam8157/gpdb,xinzweb/gpdb,edespino/gpdb,lisakowen/gpdb,janebeckman/gpdb,xinzweb/gpdb,kaknikhil/gpdb,janebeckman/gpdb,jmcatamney/gpdb,edespino/gpdb,jmcatamney/gpdb,Chibin/gpdb,lintzc/gpdb,Chibin/gpdb,kaknikhil/gpdb,yuanzhao/gpdb,greenplum-db/gpdb,rvs/gpdb,jmcatamney/gpdb,xinzweb/gpdb,greenplum-db/gpdb,kaknikhil/gpdb,Chibin/gpdb,lintzc/gpdb,edespino/gpdb,edespino/gpdb,greenplum-db/gpdb,cjcjameson/gpdb,Quikling/gpdb,ashwinstar/gpdb,cjcjameson/gpdb,cjcjameson/gpdb,adam8157/gpdb,lisakowen/gpdb,yuanzhao/gpdb,Quikling/gpdb,Quikling/gpdb,cjcjameson/gpdb,50wu/gpdb,yuanzhao/gpdb,lintzc/gpdb,50wu/gpdb,cjcjameson/gpdb,cjcjameson/gpdb,cjcjameson/gpdb,adam8157/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,kaknikhil/gpdb,cjcjameson/gpdb,jmcatamney/gpdb,edespino/gpdb,kaknikhil/gpdb,rvs/gpdb,Chibin/gpdb,Chibin/gpdb,rvs/gpdb,50wu/gpdb,cjcjameson/gpdb,lintzc/gpdb,xinzweb/gpdb,kaknikhil/gpdb,janebeckman/gpdb,yuanzhao/gpdb,rvs/gpdb,yuanzhao/gpdb,edespino/gpdb,lintzc/gpdb,50wu/gpdb,kaknikhil/gpdb,yuanzhao/gpdb