2D Toolkit 1.1 b3

[unikronsoftware]

• Sprite collections can be set up to build to multiple atlases.
• There are restrictions when this is enabled, dicing is not allowed (as the diced sprites can end up on any atlas) and the static sprite batcher won't work (for similar reasons) with these sprites.
• The main use case for this is for large numbers of animated sprites, and not having to worry where they go.