Implement receiver interface to reset target temperature in controller

[leloup314]

Using modified versions of the receiver/tranceiver classes, you can feedback the value of a QSpinDoubleBox on the receiver all the way to the controller.py in order to reset the target temperature for the PID controller. For this, the controller.py socket needs to be of type zmq.DEALER and receiver/tranceiver need to be bidirectional (see here)