Add RPi.GPIO button controlled standby event
Add RPi.GPIO button controlled standby event

At the moment bridging gpio pin 23 and gnd (aka pressing the button)
sets the standby event and the standby thread loops.
After a registered button press on pin 24 the standby event is cleared
and the standby thread waits. The old stop_standby() is renamed to
kill_standby().

timo95/Analog_RGB_Driver,timo95/Analog_RGB_Driver