More Performance Tuning (0.22.1 Alpha)

This update brings a nearly complete re-write of the code responsible for interactions between Actors and blocks or fluids.  This should have much better performance.

Fluids, in particular, should flow much faster while on screen.  They were getting bogged down in some buggy and slow behavior.  They no longer do this.

You should see much better performance while moving the view around, as well.  Previous to this update, moving the view caused the physics system to rebuild it's version of the terrain from scratch.  Now it's hanging on to that data and reusing as much as possible.

The one area where you'll still see poor performance is when there are an excessive number of actors on screen, especially when they're interacting with fluids.  This is something I'll likely never be able to fix, at least without giving up some of the fun physics features of the game.

Have fun with the new update!