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/trunk/MailerContrib@17412 0b4bb1d4-4e5a-0410-9cc4-b2b747904278