OP-1139: fix wrong sign for bias and some optimizations

+review OPReview-598
Merge branch 'amorale/OP-1139_baro_2nd_order_compensation' into amorale/OP-1149_gyro_accel_thermal_calibration
OP-1150 UI for thermal calibration: calculate variance before and after calibration as sanity check
OP-1150 UI for thermal calibration: Zero gyro/accel calibration before acquisition