Deal with joints not in the planning group

[kamiradi]

Bound the joints of the robot that are not part of the planning group.

One last comment on this -- when I looked at Meshcat, the gripper fingers definitely fly all over the place (which might be why I had to bound the velocity/accel/jerk to finite values, else the gripper fingers might have flown into collision or sparked another silent failure).

I think what we need to do is take all of the joints that are not actively part of this group, and constrain their positions to exactly the starting positions + velocities and further derivatives to zero.

Originally posted by @sea-bass in #52 (comment)