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

[srayner]

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.