Add kinematic objects to Cannon

[diarmidmackenzie]

Offshoot of #15.

Possible (modest) perf improvement to Cannon wrapper by not syncing positions of static objects to the physics engine (cos they are static, so should never move).

Requires introducing a distinction between kinematic & static objects (as per the Ammo driver), which doesn't currently exist. Kinematic objects will require syncing to physics every tick. That will be the only difference.

The relevant part of #15 quoted here for convenience:

Cannon doesn't distinguish between kinematic & static objects. So you could say that all static objects in Cannon are kinematic - hence we should update them every frame.

We could introduce a "kinematic" concept at the wrapper level in Cannon, where the sole difference between static & kinematic would be that kinematic objects would have their position sync'd to the physics engine every frame, whereas static objects wouldn't.

I'd suggest a new issue to track that potential improvement. That said, I'm not sure there's that much value as the before/after phases are already much cheaper relative to the engine with Cannon than they are with Ammo.