ENG-6854: Refactor catalog group schema generation code to be saner.
ENG-6854: Add ADMIN permission and SYSPROC is an alias of ADMIN.
Remove redundant permission check from ClientInterface.
ENG-6854: As Izzy pointed out, we can actually remove sysproc from the
spec.

The aliasing is done in Java when Volt parses the DDL and constructs
the Permission object.
Merge pull request #1741 from VoltDB/ENG-6854

ENG-6854: Add ADMIN permission.

r=akhanzode