HIVE-8141: Refactor the GraphTran code by moving union handling logic to UnionTran [Spark Branch] (Na via Xuefu)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/spark@1625642 13f79535-47bb-0310-9956-ffa450edef68
HIVE-8160: Upgrade Spark dependency to 1.2.0-SNAPSHOT [Spark Branch]

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/spark@1625860 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'upstream/spark' into spark