TAJO-1259: Change tsql history behavior. (Jaewoong Jung via hyunsik)

Closes #316
TAJO-1249: Tajo should check if a file format given in DDL is supported. (DaeMyung Kang via hyunsik)

Closes #313
TAJO-1268: tajo-client module should not use UserGroupInformation.

Closes #318
TAJO-1267: Remove LazyTaskScheduler. (DaeMyung Kang via jihoon)
TAJO-1266: Too many logs when writing a parquet relation. (DaeMyung Kang via jihoon)

Closes #320
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into index_support
Merge branch 'index_support' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-838_3
Added documents