[SPINE] Fixes broken examples + bug fixes

The last spine update broke the spine examples, this fixes them with the following notes:

- The spine API has changed slightly (now supports "tracks" for animations, delayed animation queuing, etc)
- The PIXI API has changed slightly (`setInteractive` has been replaced by the `interactive` property)
- Both spine and TexturePacker can export `.atlas` files so that's the default format, also they support multipage atlases and are loaded automatically.
- FFD animations seem to be broken at the spine runtime level, I will open an issue with them, in the mean time avoid using them.

Cheers!