Fixes the "Command's Approval Rating" stat in rev end-round reports

The issue was that it was always reporting as 100% because it had problems counting revs.

It's also been moved to auto_declare_completion_revolution() so it prints in non-rev rounds as well if there were any headrevs that round.
Merge pull request #4931 from Ikarrus/approvalrating

Fixes the "Command's Approval Rating" stat in rev end-round reports