Add Simple Physics Support

[davesmith00000]

You can build games like platformers without a physics engine, but it's pretty inconvenient, because a lot of the code you end up writing is the same code you'd expect to see in a rigid body physics library, and has the same determinism guarantees (few).

Initial thoughts are that this isn't a core part of the engine, it's just a simulation you plug into your model or view model, and call update on. The view can then ask the simulation where things are now and draw them.