Add support for SQL DISTINCT on multiple columns and expression
Add sql coverage tests for DISTINCT on multiple columns and expression; Fix the existing unit tests
Add the fix for DISTINCT on table aggregate
Merge branch 'master' of github.com:VoltDB/voltdb into ENG-6436-distinct-reroute
Merge pull request #1794 from VoltDB/ENG-6436-distinct-reroute

Eng 6436 distinct reroute
Squashed commit of the following: update on VMC
commit a4f74b9ac92ee0b524fba581f05c5f856632859c
commit acdca6a660091b7feaa2e42efad022bdef96b3a9
commit f24d3c24262e6c30047dc8d2deae3fc254258d4b
commit 4484f2fc751bde1c4b81b62f0556a0220d574c97
commit c3b42b5c9dd82e6f9f9dac46cf70b837566f4ab8
Merge branch 'master' of github.com:VoltDB/voltdb