Always use polling mode for CO2 operation: In the previous version the CO2 sensor was operated in streaming mode (2 measurements a second) in case it was used stand alone (without multiplexer). This added some complexity to the implementation (setup, error handling etc). To reduce this the sensor will now always be operated in polling mode like it is done for multiplexer operation. To make sure that the correct mode is set a command has been added to the configuration steps.