Remove unused QueryController.

This was part of the obsolete query queue system.
Remove lingering remnants of obsolete "translator" interface.

This was obsoleted by Transifex.
Remove obsolete query_cache configuration options.

Much new code expects the query cache to always be present, especially
for stuff that is 100% Cassandra based and doesn't even have a Postgres
query to back it. These options are just cluttering up our code since
they're useless now.
Fix sr_moderator_invite_quota not being parsed correctly.
Remove various unused configuration settings.
wiki: Correct /wiki/revisions route priority.
wikitoc: Fix some headers ending up at the wrong level.
Change commented -> comments in api docs