Remove FOF dependency in twofactorauth plugins

This PR removes the dependency on the FOF library within the TwoFactor Auth plugins. It moves a few of the required classes into the core of the CMS in accordance with the GPL licensing of the code.

Tracker: http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=33604&start=0