HOTFIX: RSS Feed Reader Improvements

We have made numerous improvements to the RSS Feed Reader widget to protect against various error conditions.

Now, it will validate that the URL entered for the widget contains a valid RSS feed both when loading and when saving the values.

It will also protect against feeds that timeout or are unreacheable. It allows up to 10 seconds for the feed to initially download before timing out.

Subsequent requests for the widget will load locally from the cache and will not require the full 10 seconds to load, until the cached copy of the feed expires.

The contents of the feed are cached locally for 15 minutes.

Additionally, better error notification is included, both in the UI on the front end, as well as adding a feature to email the store owner once approximately every 15 minutes should errors be encountered while loading the feed.