moving forward will open up many nice opportunities. This will be used for the media accessor in the new DynamicDocument.
Renamed XmlPublishedContentStore to just DefaultPublishedContentStore.
Made GetProperty an extension method for IDocument and removed from the interface as it is not needed there.
and is poorly formatted, this now allows us to properly abstract an IDocument using the new IContentStore which now
returns IDocument instead of XmlNode so we now have an abstraction away from Xml for routing.