Improve CO2 calibration: The most common calibration environment for diving is fresh air => ~400ppm co2. Some sensors do not have this setting as default => Calibration to 0ppm. To make sure that a proper calibration reference is set the common used value of 400ppm is not set before starting the calibration. For implementation new states were added to the co2 protocol state maschine. In addition the rx processor is now able to handle two responds parameters.