TAJO-279: Improving the query_executor page of web UI. (Wan Heo via jihoon)
TAJO-290: TajoDataType.Type.NULL should be NULL_TYPE. (DaeMyung Kang via jinho)
TAJO-341: Implement substr function. (hyoungjunkim via hyunsik)
TAJO-207: Implement bit_length(string) function. (DaeMyung Kang via jihoon)
TAJO-345: MergeScanner should support projectable storages. (jihoon)
TAJO-207: Implement bit_length(string) function. (fixed a missing log in CHANGES.txt)
Merge branch 'master' of http://git-wip-us.apache.org/repos/asf/incubator-tajo into DAG-execplan