Adding loadByPsr0 to JLoader

This PR adds the ability for developers to integrate PSR-0 compatible code into their applications, such as that from the new Joomla Framework, and allow it to be registered properly to the autoloader.

Tracker item for this is here: http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=30525