Added Windows Phone 8 ANID2

For reference see: http://msdn.microsoft.com/en-us/library/microsoft.phone.info.userextendedproperties%28v=vs.105%29.aspx
I've already merged this change, but noticed this is using the `btoa()` function which exists in the browser but not in Node.

Is there another way this can be done so it will work on Node as well? Currently this method throws an error on Node that `btoa()` is undefined and not a function.