WPSymposium - 1st pass update

* Cleans up PHPDoc for WPSymposium Converter
* Fixes Forum slug field mapping
* Add Topics section
* Adds Reply Section
* Adds callback_topic_status for open or closed topics
* Adds callback_sticky_status for sticky topics
* Adds reserved callback callback_forum_type to be implemented
* Adds reserved callback callback_forum_status to be implemented