ENG-2549 order by compound key index with equality filters
Merge branch 'master' into ENG-2549-use-index-order

Conflicts:
	tests/scripts/plannertester/ENG-2549/baseline/ENG-2549.plan0
ENG-2549 add edge cases for indexed-based order to TestPlansOrderBy
ENG-2549 added comments re: review by jhugg.
Merge pull request #502 from VoltDB/ENG-2549-use-index-order

Eng 2549 use index order