[gps] Add a new GPS based on the datalink
[fms_network] Added multicast support
[ground_segment] Added NatNet to ivy service
[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
[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
Merge remote-tracking branch 'paparazzi/master' into testing_irridium

sync with master