fix attachments AJAX when friendly URLs are disabled
add a way to pass raw expressions to the SQL query builder
fix #124. the problem was that posts made at the same time could un-sync the conversation countPosts field (so it was 1 less than it should be.) so, to fix the sync issue on an existing forum, the upgrade script needs to be run. this can be done by enabling the Debug plugin and clicking "upgrade database" in its settings.