Update real multiplexer implementation: The final multiplexer provides 4 sensor connections instead of three supported by the prototype => A mupping functionality has been introduced to map the 4 possible mux addresses to the three visible O2 sensor slots. In addition the request cycle time is not depending on the number of sensors connected to make sure that all sensors are read within a defined time frame. The error reaction had to be updated to reset mux channels if one of the sensors fails to respond.