Fix for issue #112 - only decrement reply count for forums.

The reason this is deceremented for forums is that the thread starter
is also a comment and is counted in the SQL as a reply.

Other forums don't have a 'comment' thread starter so their reply count
is correct.
Moved comment count manipulation to accessor in Result::Comment
Merge pull request #115 from jbarrett/issue112-comment-counts

Fix for issue #112 - only decrement reply count for 'thread' forums.