Physics Properties Organization

Currently, the physics settings in the properties panel works, but it gets messy at times, especially when dealing with multiple physics systems and particle systems at the same time. It's not a massive problem, but I thought I may as well take a shot at making it consistent.

First, I've moved everything into one Physics panel, because particles and hair are really just another type of physics. The box at the top keeps everything nice and organized, so we're only working on one physics system at a time. I've also separated out hair because it is becoming increasingly separate from particles.

However, some types of physics can be applied multiple times to objects (particles, hair, dynamic paint) while others cannot (Smoke, Rigid Body, Collision, etc..). So to avoid confusion, the systems that cannot be added again are grayed out when adding a new system.

Lastly, the Type setting would be consistent across all physics types instead of being one way for smoke, one way for dynamic paint, and yet another way for rigid bodies.