Loader can now natively load XML files via `load.xml`. Once the XML file has loaded it is parsed via either DOMParser or ActiveXObject and then added to the Cache, where it can be retrieved via `cache.getXML(key)`.

Cache now has support for XML files stored in their own container. You can add them with `cache.addXML` (typically this is done from the Loader automatically for you) and get them with `cache.getXML(key)`. There is also `cache.checkXMLKey(key)`, `cache.checkKeys` and `cache.removeXML(key)`.