Updating FOF to version 2.2.0

# Joomla! RAD Layer (FOF) updated to version 2.2.0

## Overview

A major new feature is included. An ORM-like interface to accessing table relationships in FOFTable with a matching iterator to step through a Model's item list loading only one record at a time (using database cursors). This will help developers access records in a one-to-one, one-to-many and many-to-many relations using an architecturally more sound way. It's still not architecturally ideal of course as FOF follows the same convention as Joomla!, breaking its data model between a table and a model class and it's unlikely that will change due to backwards compatibility concerns.

For the complete changelog please consult [the FOF changelog](https://github.com/akeeba/fof/blob/development/CHANGELOG).

## Backwards compatibility

This PR is fully backwards compatible with the Joomla! RAD Layer (FOF) introduced in Joomla! 3.2.0.

## Testing instructions

**Time investment: approximately 2 minutes**

Apply this patch. Make sure that the "Post-installation messages" component and the Two Factor Authentication feature using Google Authenticator are still in working order.

## Acknowledgments and thank you's

This release would have not been possible without the FOF contributors @roland-d @wilsonge @tampe125 @bbloom @jurianeven @peterpeter @Eighke @anibalsanchez @Skullbock @pagchen @willfaulds @zanardigit @dadaxr and everyone who participated in the mailing list discussions. I hope I'm not forgetting anyone.

The author would like to make a special acknowledgment to the Laravel Framework for acting as an inspiration of the relations handling. Also a special thank you to Herman Peeren for infecting me with the bug of looking into ORM more seriously.