Item12786: Improve topic matching for MailerContrib

When subscribed to multiple topics in WebNotify, also parts of topics
where matched, eg.
   * UserName: TopicA TopicB TopicC
matches TopicBX and XTopicB

git-svn-id: http://svn.foswiki.org/branches/Release01x01@17414 0b4bb1d4-4e5a-0410-9cc4-b2b747904278