- Added the GraphicsDevice.BackBufferSize property.
- Removed the view/projection parameters from PrimitiveRenderer.Begin.
The PrimitiveRenderer now automatically takes the view/projection matrix from
the currently active camera in the scene.
- Added the Camera.ViewProjection property.
- Added a new class "LitMaterial".
- Added some constraints to the properties of the Light class.
- Improved and completed the Diffuse.fx effect code.