(force/torque sensor needs new API)
in a nutshell, users of shared memory physics API should not
directly poke into shared memory, not fill 'SharedMemorCommand'
nor read SharedMemoryStatus directly. The C-API declares 'handles' for those,
to avoid it from happening.
(load urdf, get state, set desired state, step simulation)
Create SharedMemoryCommand and put that into the queue
move arrays for Q, Qdot etc into the command
