* Background canvas is now decoupled from the window. It can now be
sized independently of the window.
* Canvases/Sprites now have their own textures that must be
initialized with the renderer prior to them being used. This is
all handled by DotSDL.
* A SpriteList class has been created to maintain collections of
Sprites, replacing the old List<Sprite> system. This was required
to ensure that the Sprite textures are properly allocated and
freed during creation/destruction.
* Background clipping now functions as expected. The background
Canvas can now be cropped and scrolled at will.
* Background rendering has changed from directly blitting the canvas
onto a texture to using an intermediate target texture.
* Updated the Sample.Sprites project to test/demonstrate the new
Canvas features. Project is still incomplete.