[SQL] Break hiveOperators.scala into multiple files.

The single file was getting very long (500+ loc).

Author: Reynold Xin <rxin@apache.org>

Closes #1166 from rxin/hiveOperators and squashes the following commits:

5b43068 [Reynold Xin] [SQL] Break hiveOperators.scala into multiple files.
HOTFIX: Fix missing MIMA ignore
HOTFIX: Add excludes for new MIMA files