Item12650: Improve handling of deprecated plugins

Group the deprecated plugins into a separate heading in the
configuration, and set them to EXPERT mode.  They'll be hidden unless
the checker flags a warning or error.

git-svn-id: http://svn.foswiki.org/trunk/JQueryPlugin@17078 0b4bb1d4-4e5a-0410-9cc4-b2b747904278