Use Bb code parse cache for bb code tagging

This pull request allows BBM to use the bb code parse cache which is avaliable Xenforo 1.2 upwards's

Posts & signatures can have a "message_parsed" or "signature_parsed" which contains the bbcode parse tree outputted by the parser. In the future, other things (private conversations) may also support bbcode parse tree caching.

Testing some complex pages renders reduces _createBbCodesMap runtime under xdebug from ~200ms to 2ms on a VM with 4gb ram, running on a fairly idle Xeon E3-1220.