camtrack: camera tracking module

- Initial structure for camera tracking module
  - Add initial structure for module
  - Use MPImage to render RTSP stream
- Subclass MPImage to allow tracker overrides
- Abstract an interface for the tracker and provide dlib example
- Enable title
- Add cv2 CSRT tracker
- Document TODOs
- Rename image to tracker_image
- Add tracker to forward mavlink commands
- Add dev notes
- Add requests for camera and gimbal info
- Preparation for sending mavlink camera track commands
- Add event class and enums
- Remove event class and simplify
  - Note: mp_image has a different event model to param_edit etc.
- Add mavlink cmds to start / stop tracking
- Capture command_acks
- Add variables for camera and gimbal sysid and compid
- Add initial onboard controller script
- Remove print of command_long
- Add handlers to onboard controller
- Format ack messages
- Format debug messages
- Onboard controller: send camera info
- Onboard controller: use enum for flags
- Add onboard controller and gimbal controller classes
  - Fix missed lock -> _lock rename
- camera_view: remove hardcoded tracking coords
- onboard controller: add video capture and tracker
- camera_view: disable repeated discovery requests
- onboard controller: update controller gains
- camera_view: add example RTSP URLs
- camera_view: suppress mtype checks
- onboard controller: thread safe handling of mavlink messages
- camera_view: fix handling of image resolution when setting track rectangle
- onboard controller: suppress profiling output
- camera_view: additional mavlink debug info
- onboard controller: additional mavlink debug info
- onboard controller: add command line options
- camera_view: add command line options
- onboard controller: add usage docs
- onboard controller: initial support to send tracking image status
- camera_view: enable one time discovery requests
- camera_view: use MAV_CMD_SET_MESSAGE_INTERVAL to request image status
- onboard controller: populate image status using initial target
- camera_view: tidy module docstring

Signed-off-by: Rhys Mainwaring <[email protected]>

Author: srmainwaring