[gps] Add a new GPS based on the datalink
[fms_network] Added multicast support
[ground_segment] Added NatNet to ivy service
Activate the use of the barometer by default on the lisa S.
Merge pull request #681 from karlito139/baro_lisa_s

Activate the use of the barometer by default on the lisa S.
[ardrone] Updated gains and reference model for inside
[modules] Added a module for following based on received remote GPS
[follow] Fixed following module
[datalink] Fixed some small issues with UDP datalink
[chibios] fix compilation with chibios

was broken when moving generators due to tricky dependency effect
[conf] remove obsolete BARO_HAS_BOARD defines
Merge pull request #648

Full optitrack implementation.
Only AHRS GPS frequency scaling needs to be implemented to fix the issues with using the optitrack for heading.

Added gps based on information gathered through the datalink
Added ground module to transmit optitrack packets to the drone
[math] fix resolution in ltp_def rotation matrix
[ground_segment] add libprcre to natnet
[actuators] actuators driver that generates dual pwm pulses.

Added an airframe file for the delfly.

Shared some functions and declarations between the regular PWM actuators and the dualPWM actuators.

closes #678
[actuators] dualpwm fixes for nps
Use PPM [usec] values for radio config files with SBUS
[ins] IIR filter replacing mean in hff

(Second order Butterworth) implementation for INS subsystem.

closes #677
[ins] hf_float: fix compilation with GPS_LAG
[ins] hf_float: remove inline from functions