Updated FOF to version 2.1.1

# Executive summary
This PR updates the Joomla! RAD Layer to FOF 2.1.1, released on December 14th, 2013. FOF 2.1.1 contains several bug fixes and is more rigorously tested than previous versions.

# Test instructions
After applying this PR check that the post-installation messages and the two-factor authentication features in Joomla! are still working as expected.