TAJO-953: RawFile should release a DirectBuffer immediately. (jinho)

Closes #79
Fixed wrong table syntax in sphinx doc.
 TAJO-956: CONCAT should be support multiple params and null param. (Hyoungjun Kim via hyunsik)

 Closes #81
TAJO-960: TajoCli's problem does not show the current status.

Closes #83
TAJO-955: Add database selection submit button in catalogview.jsp for text based browse. (Hyoungjun Kim via jihoon)
TAJO-961: TajoCli should exit when at least one query faces error while executing a SQL script. (hyunsik)

Closes #84
Merge branch 'master' of http://git-wip-us.apache.org/repos/asf/tajo into TAJO-837