Added Transform

- SpriteTransform now derive from Transform
Added Transform to IDrawable.Draw

- To uniformize the Draw interface for composites
Minor changes for GamePrototypes

- Added DrawContext.FillRectangle
- Fixed Transform when not Rotation involved
- Added GetSpriteAnimationTemplate and GetSpriteCompositeTemplate on
SpriteSheet
- Added GetTemplate to get any kind of ISpriteTemplate on SpriteSheet