Added xRotation and yRotation to JoystickPlugin to fully support Xbox One controller

The native PC driver for the Xbox One controller maps the right stick to rotation X and rotation Y, which is currently not exposed by the `JoystickPlugin`. This change adds those two properties, which are already supported by `SlimDX.DirectInput.JoystickState`, and has been tested with a real controller. The left stick, D-pad, buttons, triggers, and bumpers already work, too.

http://majornelson.com/2014/06/05/pc-drivers-for-the-xbox-one-controller-available-now/