Adding code to make it easier to register controls with the JavaFX
scene.
Rewired the key actions a little bit. The developer should have access
to the underlying KeyEvent in case they need things like Alt or Ctrl key
pressed.
Added rudimentary mouse controls. We still need a better way to request
mouse-based events that does not encourage switch statements.
Added an enumeration to expose only the mouse events that are currently
supported. It also makes it easier to respond to different mouse button
presses without adding logic to the custom input handler.