Pull BEE ADIO control (gatevalve/SAM power) out into own actor.

Control of the gatevalve and SAM power is done via a kernel module and a thin cython shim, both in ics_xcu_rtdADIO. When the controlling program (the xcuActor) exits or the device is closed, the H4 DAQ is powered down and the gatevalve is closed. Both of these can be annoying/surprising/troublesome/problematic, especially after a recent change to the SAM/BEE power board.

I think factoring the gatevalve and SAM power control off into a tiny and stable actor would help significantly. The interface is tiny: we are flipping or reading four bits via very few commands (sam on/off/status, gatevalve open/close/status).