Care Free mode
care_free_heading in stabilization.c
[rotorcraft] add CareFree mode to settings/gcs
[rotorcraft] care free mode

- still not implemented for stabilization_euler
- move read_rc_setpoint_* functions to c file
- add GUIDANCE_H_MODE_CARE_FREE mode
- add stabilization float_euler subsystem
- use normal stabilization subsystem in NPS instead of hardcoded euler
care free mode for euler
removed todo euler care free
improved care free euler
fixed misplaced brace
[gcs] display settings to be saved as integer with correct format
[gcs][settings] nicer popup warning about parameters not in the airframe file
[gcs] fix rounding of values
[modules] fix sonar_adc doc
[stm32] throw an error if trying to USE_I2C0
[i2c] convenience functions return i2c_submit success
[xsens] Commenting
[actuators] mkk: if submit fails, start at last one next time
[sim] don't include ocaml stuff for jsbsim target
[rotorcraft] AHRS_EULER_INT message only for CMPL_EULER
Merge branch 'care_free_mode'

New "care free" mode that keeps the yaw ref pointing in initial direction:
AP_MODE_CARE_FREE_DIRECT: otherwise like the normal ATTITUDE_DIRECT mode.
CARE_FREE is implemented as a horizontal submode: GUIDANCE_H_MODE_CARE_FREE
so it could be combined with other vertical modes as well...

Other changes:
- move read_rc_setpoint_* functions to c file
- added missing modes to settings/telemetry
- add stabilization float_euler subsystem
- use normal stabilization subsystem in NPS instead of hardcoded euler

closes #390 and closes #391
suppress compilation warning for px4flow