[ahrs] add float multiplicative quaternion linearized Kalman Filter
[modules] digital_cam: dc_buffer is uint16, set max number as default DC_IMAGE_BUFFER
[energy_ctrl] fix dt
[energy_ctrl] output is v_ctl_pitch_setpoint, not nav-pitch anymore
[energy_ctrl] Airspeed slew always active because of defines at start. Remove confusion.
[energy_ctrl] warning if STALL_AIRSPEED not defined

Stall airspeed is automatically protected (+23%) with unexpected high airspeed when not defined... At least warn the user
[lib/ocaml] fix float conversion on ARM

On architectures/platforms where doubles need to be aligned,
link was throwing a Bus error since the floats in the received message are not aligned.
Now it just copies floats/doubles byte by byte to avoid this issue.

This should fix #421