Animation Component Updates:

- The Animation Managers 'isPlaying' property is now a more accurate representation of if an animation is playing or not.
- Callbacks assigned to animations are now dispatched after the cells of entities are updated.
Signals for each individual Animation are now only created when accessed, thus preventing a huge creation a unneeded signals that may never get used.
Animation Manager Updates.

- Added FOUR new Kiwi.Signals
    - onPlay - When an animation is played.
    - onStop - When an animation stops.
    - onUpdate - When the cells of the sprite the animation belongs to updates.
    - onChange - When the current animation changes.
- Fixed minor issue with 'switchTo' method where if told to play it would switch to the animation twice.
Actually added in the AnimationManager in the commit