(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.
need to add streaming because memory is too small to store all lines
initial test of PD control in physics server, need to switch to PD control for motor constraint, instead of using external forces.
only allow server to create and initialize shared memory,
client will report failure
intercept signals to cleanup shared memory in standalone app, thanks to
Roland Philippsen.
