TAJO-829: Same constants in groupby clause may cause planning error.
TAJO-801: Multiple distinct should be supported. (Hyoungjun Kim via hyunsik)
TAJO-811: add simple fifo scheduler support. (jinho)
completed parquet reader and added the example of the vectorized tuple iteration model.
Refactor boolean and null vector.
added initial work for jit vec physical planner.
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into CodeGen
added cukcoo hashing.
improved cukcoo hashing.