Yet more separation out of the physics code. Branch ordered now handled separately from force application.
Yet more separation out of the physics code. Branch ordered now handled separately from force application.

git-svn-id: 68167fd1bfb998e667cdedbd5f57838adff51fff@37 46b6b11e-c11a-0410-a857-b1ddefb2cc20

dogriffiths/hipster,dogriffiths/hipster,dogriffiths/hipster