Item12699: Remove cgisess file when removing a user

Otherwise it's possible that the user can continue to update topics due
to the existing session.

git-svn-id: http://svn.foswiki.org/trunk@17538 0b4bb1d4-4e5a-0410-9cc4-b2b747904278
Item12699: Add remove cgisess to AntiWikiSpamPlugin

git-svn-id: http://svn.foswiki.org/trunk@17539 0b4bb1d4-4e5a-0410-9cc4-b2b747904278