Replaced old AI code with a new one that uses a behavior tree.
The behavior tree is from 3rd-party code, and also makes use of Hump (for LOVE2D) for Class instantiation;
some of the Hump files are probably not needed.
Player class now has a AIController variable, since when coding this I could not figure out how to make AI an extension of the Player class. Perhaps will do that in the future.
Update and GameController code reflect the above changes as well.