Avatar simulate optimisation

Don't recompute the transform and the rotation if the local and parent transform didn't change.
extractRotation being what takes most of the time in otherAvatars/simulate, avoid calling it when it is not necessary.
Actually this is even better I spend between 3 and 4.5 msec in othersAvatars/simulate with 20 dancer.js in view as opposed to 5/6 with micro threading and 11/14 when I started working on that.