Initial commit of feed package.

Moving some parsing logic around and starting to think about how I want
to make this thing extensible.

Cleaning up some things.

Adding some things for testing.

Updating @since tags and general cleanup.

Cleaning up unit tests.
Tests for JFeed
Fleshing out a lot of unit tests.
Adding tests for JFeedParser
Tests for remaining feed code.
Finishing up the RSS parser implementation.
Update the feed package for deprecation of `JXMLElement`.
Move feed package tests to the new unit test structure.
General cleanup.
Update libraries/joomla/cache/controller.php

Solving Strict standards issue in CMS
Update libraries/joomla/cache/controller/page.php
Update libraries/joomla/cache/controller/page.php
Update libraries/joomla/cache/controller.php
Update libraries/joomla/cache/controller/page.php
Merge pull request #1622 from LouisLandry/feed

New Feed Package.
Merge pull request #1710 from infograf768/patch-7

cache strict standards issue when using system plugin cache in CMS
Merge pull request #14 from joomla/staging

Staging