Simplify and improve the logic used to manage Token animation by taking advantage of the new TokenMesh data structure.

[aaclayton]

There is no meaningful API change for handling Token animation that results from this change, but there is one minor change which is technically breaking if this method was being used by an external package.

Token#getDisplayAttributes has been moved to TokenMesh#getDisplayAttributes, so if you were previously calling token.getDisplayAttributes() you now need to call token.mesh.getDisplayAttributes(). It is not intended that this function be used by external code though, so if you are using this function you may wish to consider if it is necessary to do so at all.