New features for tracking number of threads, number of posts, last post and number of message page views.

This pull covers the following broad changes;

* New visit entity with mapper and hydrator, for keeping track of message views (page visits).

* Added properties to Tag Entity for number of threads, number of messages and last post.

* Modified so you can now create new threads.

* Added css classes to form and created a view helper to make the form compatible with Bootstrap3 out of the box.

* Some minor code clean up.

Still to do:

* Review the factories in the discuss service to make sure they all use config options and not hard coded class names.