Move frontend autoload classes into a separate method.
Force bbPress so site is always seen as public. Fixes #56.

* Add new file - frontend-bbpress.php
* Add class - 'CBox_BBP_Site_Public' - to override bbP's site
visibility so forum-related activity can be recorded by BuddyPress.
Add class to 'autoload' array.
Update phpDoc for frontend-ges.php.