Fix moderator detection.

It seems that VBulletin membergroupids have changed.  ID 7 no more
means a moderator - instead all moderators have 2 and dev team
has additional ID of 19.

The mapping of membergroupids to moderator status is now done just
once at login time.  Previously the group number was checked whenever
one wanted to determine moderator status, although a boolean moderator
field had been set at login.

Additionally fixed emailHash saving in ForumUser#clientUser - previously
the result of calculation was just thrown away.