Switched queries to JSON + fixes.

* Switched from XML to JSON queries. I didn't even realise VLC did JSON.
* Huge improvements to effeciency and size of code thanks to JSON.
* Moved almost all $.ajax requests into a single function, resulting in
smaller js file size, extra code reuse, and some minor problems fixed.
* A new set of refresh..() commands will not NOT be executed for each
playlist item change.
* Extras, Platlist & File Browser now fade in/out.
* Added more AspectRatio options, as per the VLC API spec.
* Added mpg to video formats list.