Rewrite

Move thread, forum, category, and reply all to their own classes in their
own files
Use an easier error system
Perform checks for errors, rather than wrapping in hundreds of ifs
Extend ContextSource
Naming scheme: get*() returns raw data, probably from db, show*() returns
proccessed text/html
Move some GUI functions to thread/forum/category
Stop CSS loading on every page(!)
Change url format to allow easier selection in SpecialWikiForum.php, that
was a real mess. Now like Special:WikiForum?wfaction=editforum&forum=1
Remove code to add WikiForum to toolbox, it doesn't work, and it would
make more sense for wiki administrators to add this to the sidebar anyway
Docs!!!
Simplify searching code
Remove SQL user_text columns
Remove SQL deleted columns, instead actually $dbw->delete() the rows
Simplify sorting and limiting code
Functions return strings, not objects

Change-Id: Ica775eb72c629a6a4bf8e00ad49831656e11da21