TAJO-897: PartitionedTableRewriter is repeated several times with same table. (Hyoungjun Kim via hyunsik)

Closes #54
TAJO-898: Left outer join with union returns empty result. (Hyoungjun Kim via hyunsik)

Closes #55
TAJO-905: When to_date() parses some date without day, the result will be wrong. (hyunsik)

Closes #57
TAJO-902: Unicode delimiter does not work correctly. (jinho)
Closes #53
TAJO-911: Refactoring Mysql/Maria Catalog Store. (DaeMyung Kang via hyunsik)

Closes #59
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-774_2
Added missed hashCode and equals to WindowAggNode and WindowSpec.