ENG-4625 fix leaks and logic errors in matview min/max and matview nullable aggs
Merge pull request #844 from VoltDB/release-3.7

Back-merge from Release 3.7
Merge remote-tracking branch 'origin/release-3.7' into ENG-4625-change-catalog
ENG-4625 / ENG-5291 beef up tests that missed these issues.
ENG-4625 code styling re: r=xjia
Merge pull request #843 from VoltDB/ENG-4625-change-catalog

Eng 4625 change catalog