New OOP Engine

Some things don't work now, but loading and creating worlds is now like
20 times faster, because I recoded the OOP API.

Before, classloader loaded the classes every time a new instance is
created, now it just saves the file in the classes table and runs it
when a new instance is created.
(loadstring is one of the slowest lua functions)

There were other improvements - mostly in performance aspect - in the
classloader API.