TAJO-449: Implement extract() function (Keuntae Park)
TAJO-526: HCatalogStore Documentation. (jaehwa)
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/incubator-tajo into TAJO-539
add hasUnion and add createTwoPhase.
Refactored many things.
added comment.
comit for moving workplace