TAJO-972: Broadcast join with left outer join returns duplicated rows.(Hyoungjun Kim via jaehwa)

Closes #89
Merge branch 'master' of https://github.com/blrunner/tajo into TAJO-704
TAJO-969: Distributed sort on a large data set may result in incorrect results.

Closes #87
TAJO-914: join queries with constant values can cause schema mismatch in logical plan.

Closes #78
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-704