[ODE] multiple collision and "shivering"

[Anselm Hook]

> ...certainly the system will look much more stable but I don't think that
> "shivering" will disappear.
> I have thought a simpler approach: when an isle is "almost stable" you can
> put its bodies to sleep ( avoiding to compute pos. and orient. every step)
> and when a body hits a sleeping isle it wakes up all the bodies of that
> isle.

> I suspect that Havok does somethink like that: when a system with lots of
> stacked bodies is stable,

Partitioning the graph is a good idea, something that Havok said they do,
and looks like something Russ mentioned as a 0.04 goal.  Requires tracing
the connectivity between connected or potentially connected bodies - and
if the group is stable to then consider turning it off.  A related benefit
(aside from turning found groups on or off) is that the solver can
integrate smaller subsystems faster than it can integrate a whole system
at once.  It's a worthwhile piece of code to write.