TAJO-1101: Broadcast join with a zero-length file table returns wrong result data.

Closes #184
TAJO-1103: Insert clause of partitioned table loses some FetchImpls. (jinho)

Closes #186
TAJO-1010: Improve multiple DISTINCT aggregation. (Hyoungjun Kim and jaehwa)

Closes #136
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-1102

Conflicts:
	tajo-core/src/test/java/org/apache/tajo/engine/query/TestJoinBroadcast.java