TAJO-1048: Missed use of session variables in GlobalPlanner.

Closes #146
TAJO-948: 'INSERT INTO' statement to non existence table casuses NPE. (Jongyoung Park via hyunsik)

Closes #142
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-1030