Almost there

XamlAnimatedGifRenderer should be minimally complete, now to hook it up
into the test app.
Minimal compilation, initial WRC implementation

XamlAnimatedGifRenderer is now a ref class and is mostly componetized:
- Only WinRT types in public methods
- Renderer owns DeviceResources and also hooks up most event handlers on
behalf of the caller
- XamlAnimatedGifMain is basically dead, still need to port over
IDeviceNotify functionality.