TAJO-501: Rewrite the projection part of logical planning.
TAJO-478: Add request-patch-review.py that helps submitting patches to jira and reviewboard. (hyunsik)
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/incubator-tajo into TAJO-502
Removed java.util.objects.
Fixed union10.