message: mavlink_commands: define autopilot component ID
  Most commands actually need to be sent to the autopilot, therefore, we
  need the autopilot component ID in various plugins.
diff: @@ -49,6 +49,8 @@ public:
  void do_work();
  + static const int DEFAULT_COMPONENT_ID_AUTOPILOT = 1;
  +
  // Non-copyable
  MavlinkCommands(const MavlinkCommands &) = delete;
  const MavlinkCommands &operator=(const MavlinkCommands &) = delete;
  