TK: support for tile animations

Support tile animations. The data is already loaded, it's mainly an issue of running the animations at runtime.

The animation probably runs on the tileset level. Meaning if a tile texture for GID 123 is requested, it is first checked whether that tile GID is recorded as having a tile animation.

If so, the tileset is not asked for the tile GID's texture but for its current animation tile GID texture by providing a timestamp along with the GID. That way no timers need to run to update the animations. This would also allow off-screen tiles to continue their animation, sort of.

This would have all tiles with the same animation run synchronously.

Estimation: 4 days