Removed the loop in the MultiBatch fragment shader so that it will work
in older GLSL versions.
Implemented TiledSprite rendering using the sprite batch system instead
of a dedicated renderer/shader combo. This means it will benefit from
batching, especially when using MultiBatch.
The power of two for a texture is now determined automatically and
the appropriate settings selected accordingly.
Simplified the batches by pulling out common functionality into the base
class.
TilingSprite now descends from Sprite with appropriate overrides to
ensure the behaviour remains as before.