[WIP] I renamed "newInstance()" to "create()" and continued reengineering.

I continued to work towards reengineering Entities to work with inheritance.

Also, I renamed "newInstance()" from the Creatable interface to "create()"
because it's shorter and more intuitive.

Finally, I moved the "animals" package inside the "mobs" package since
mobs are animals.

Signed-off-by: REALDrummer <conman.davey@gmail.com>