TAJO-42: Divide SubQuery into FSM and execution block parts. (hyunsik)
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/incubator-tajo into TAJO-44

Conflicts:
	tajo-core/tajo-core-backend/src/main/java/tajo/master/SubQuery.java
Removed Priorityclass , remove finishUnion method and add setRepartitionIfNecessary method.
Changed some method calls.
Almost completed, but we should design a way for appropriate number tasks.