Changed SO2 calibration routine

SO2 calibration routine now cals above and below canopy once per day.
Above canopy calibration is at 02:24 and is as follows:
Turn off above/below switching
6 min sample above canopy
8 min standard add above canopy
Turn on above/below canopy switching (which starts with above canopy)

Below canopy calibration is at 03:24 and is as follows:
Turn off above/below switching
6 min sample below canopy
8 min standard add below canopy
6 min sample below canopy
Turn on above/below canopy switching (which starts with above canopy)