Add Geofencing Support

[evan-palmer]

Is your feature request related to a problem? Please describe.
Users currently don't have access to an interface that creates geofences for their agents and swarm. This can result in fly-aways or unintentionally flying into restricted airspace

Describe the solution you'd like
Add an interface that enables Users to set geofences for their agents

[evan-palmer]

Commands that may be useful to enable this functionality include:

• MAV_CMD_DO_FENCE_ENABLE
• MAV_CMD_NAV_FENCE_RETURN_POINT
• MAV_CMD_NAV_FENCE_POLYGON_VERTEX_INCLUSION
• MAV_CMD_NAV_FENCE_POLYGON_VERTEX_EXCLUSION
• MAV_CMD_NAV_FENCE_CIRCLE_INCLUSION
• MAV_CMD_NAV_FENCE_CIRCLE_EXCLUSION
  Note that much of this functionality will be integrated when adding support for missions