added control and GPIO control and observable sensors and motion sensor
 - changed the configs a bit, new sensor config in rpi created to move
   sensor specific data into a separated config
 - Control and GpioControl to control anything attached to Gpio
 - ObservableSensor and GpioObservableSensor to allow listening for
   changes in sensor outputs rather than polling all the time
 - MotionSensorController added to wire the controls together with the
   observable sensors - right now the output is just switched on
   (currently turns on a LED)