Extend CMS controller base from framework class

[wilsonge]

Executive Summary

Extends JControllerBase from it's framework counterpart class

Detailed Summary

This extends JControllerBase from the Frameworks /Joomla/Controller/AbstractController class. This means it's implements the frameworks interface giving forward compatibility to the future when we will only use that class. In order to do this I have also had to introduce setApplication() and setInput() methods to reflect those in the frameworks class, the protected $app and $input variables are deprecated in favour of the private variables contained in the frameworks class (these cannot be used for b/c reasons)

As in 3.4 JApplicationBase now extends /Joomla/Application/AbstractApplication I have changed the typehinting in our constructor to allow anything extending this class to be injected (note the setApplication() method must still typehint JApplicationBase to be consistent with the interface unfortunately.

I've also changed the loadApplication() doc block to return a JApplicationCms as JFactory::getApplication() always returns said object

Testing

To test this PR you can see the unit tests pass and try using com_config (frontend and backend) to ensure everything there continues to work as expected - as this is the only component currently using the new MVC classes.