Implemented irr

I'm pleased to say that I've (practically) completed implementing the 'irr' module. Not the entire package, just the module. The only exception is a few IrrlichtDevice get*() methods which return types implemented by other modules which haven't been created yet; but backfilling those will be trivial once the types are available.

This module was much easier than irr.core. In part this is because the extension wrappers are more mature, and also because the types in this namespace were just much less quirky than the core types. Hopefully this trend will continue.

Up next: the irr.video module. Soon, I'll actually be able to draw something....