Fixes Forum Subsciptions

This primarily fixes forum subscriptions to be compatible with bbPress v2.5.3 and v2.6alpha

* Removes ie.css that was a theme CSS file and not a bbPress CSS file
* Updated CSS including RTL and minified versions
* Adds user profile forums subscription management  
* Updated bbpress-functions.php to be compatable with bbPress v2.5.3 and v2.6alpha

I have tested this with bbPress v2.5.3 and v2.6alpha and the Twenty Thirteen and Twenty Fourteen themes.