AntennaTracker: added boardconfig object

this allows the safety switch to be disabled
GCS_MAVLink: XML for MAV_CMD_DO_FENCE_ENABLE and MAV_SYS_STATUS_GEOFENCE
GCS_MAVLink: Generated code from message additions for autofence.
Plane: Sends MAV_SYS_STATUS_GEOFENCE and also allows GCS to enable/disable fence.
Plane: FENCE_RET_RALLY param. Plane returns to rally point on breach.
Plane: Changes needed prior to merging with master identified by Tridge.
Plane: we need 5 points for a valid geofence

the first and last points need to be the same for it to be a closed
polygon
Plane: fixed reverting modes when FENCE_SET_RALLY is enabled

we need to keep the guided destination we are using
AntennaTracker: Added supportfor manual control message to force antenna bearing and pitch in manual mode
AntennaTracker: minor cleanups in tracker.pde
AntennaTracker: remove call to set fly forward, else if the tracker is moving it will use the GPS direction for yaw instead of the compass
AntennaTracker: initial position was not being set on normal startup
AntennaTracker: added documentation about compass calibration to AntennaTracker.txt
AntennaTracker: update_GPS now sets HOME position and compass.set_initial_location on first good GPS fix
Plane: changed version to 2.79beta1
WPNav: add spline support
Mission: minor comment update
Copter: integrate spline navigation
Copter: minor format change
AutoTest: add copters spline test