Add data manager module and fence support to navigator

- Add function to geo.c to determine if global position is inside fence
- Add navigator support/commands for maintaining fence coords.
- Add data manager module to support persistence fence storage. Can
store other data, but only used for fence at this time.
- Add unit tests for data manager

src/modules/uORB/objects_common.cpp

@@ -129,6 +129,9 @@ ORB_DEFINE(vehicle_global_velocity_setpoint, struct vehicle_global_velocity_setp
 #include "topics/mission.h"
 ORB_DEFINE(mission, struct mission_s);
 
+#include "topics/fence.h"
+ORB_DEFINE(fence, unsigned);
+
 #include "topics/vehicle_attitude_setpoint.h"
 ORB_DEFINE(vehicle_attitude_setpoint, struct vehicle_attitude_setpoint_s);