Function: Merge topic handler

Function: Fix counts on topic merge

Function: Split topic handler

Function: Walks up the post_parent tree from the current topic_id, and updates the meta data of forums above it. This calls several functions that all run manual queries against the database to get their results. As such, this function can be costly to run but is necessary to keep everything accurate.

Function: Handle the moving of a topic from one forum to another. This includes walking up the old and new branches and updating the counts.