Adds initial code for basically functional forums:
* Forums landing page shows hard-coded list of Categories along with any
forums in the DB that use those categories.
* Admin: Create, Edit forums and view forums you own or have admin rights
to modify.
* Landing page forums list shows the title/description and dynamic count of
number of Topics and total number of Posts in each forum. TODO: distinct
count of Users who posted in each forum.
* Board Index page shows list of Threads (posts) with a Replies count and
Views count on each thread.
* Thread view is basically an array of Comments. Users can post, edit and
delete (their own) comments. Deleting the first comment removes the
entire Thread - the thread points to a first Comment to provide its body.
* Reply and Quote-Reply options working.
