Added AnimationState and AnimationStateData for spine-lua

It is pretty much a fast and rough translation of the libgdx AnimationState and AnimationStateData classes. It is only able to add animations by name and there are some modifications from the libgdx version with regards to overloading of functions. Other than this they should have a similar interface.

Something to note is that my lua experience is almost non-existent so it does probably not conform to best practice/standard format.