[ODE] Upright capsule joint

[David Walters]

> Has anyone had a chance to take a look at this? Any good?

I looked at it but couldn't get it to work properly without manaully
resetting angles back to zero anyway, which works without the joint
anyway - so it didn't really seem necessary, and kind of false
advertising. It's unfortunate because it'd be a very good feature to
have...

What about a common post step pass for all bodies which could be used
to run built-in angle reseting actions, or maybe run a user callback,
etc. ?  You could have an automatic no-rotation joint that way then...

Dave