[electrical] fix for negative currents

this should fix #753
[ins] allow define of VFF_R_SONAR_OF_M

closes #764
[meteo] update doc for mf_ptu module, log field names and units
 - [ardrone] added daren's mag freeze fix
[boards] lisa_m: AF remap for PWM using TIM3
 - [ardrone] daren's mag freeze fix, cleaned up acc. to suggestions
Merge branch 'master' of https://github.com/paparazzi/paparazzi into ardrone_mag_freeze
[rotorcraft] fix stabilization_attitude_ref_idx_set_omega_*
[rotorcraft] guidance_v: limit z_ref in update_ref_from_zd_sp

Limit the gv_z_ref to GUIDANCE_V_REF_MAX_Z_DIFF (default 2m) from current z position.
This should be useful if the aircraft can't follow the alitude in climb mode (e.g. when limited by max throttle).
[ground_segment] server: fix kml export
Merge pull request #767 from x75/ardrone_mag_freeze

[ardrone] added daren's mag freeze fix
[ardrone] use gpio API instead of system call
[mission] add support of rotorcraft to the  mission control module
[invariant] invariant filter less verbose by default
no certificate check in update google maps version

closes #772
[rotorcraft] add speed sp to GUIDANCE_H_REF_INT message

closes #763
[rotorcraft] use roll/pitch RC deadbands in attitude mode
[rotorcraft] guidance_v: only limit throttle if RC ok

This fixes failsafe if no RC or joystick present.
Thanks to evandersman
[flight_plan] Flight plan for indoor optitrack system
[conf] ardrone optitrack tuning