These use OpenGL implementation which prevented moving to ANGLE
support. Since they are rarely used they are being remove instead of
being upgrade.

- New MissionManager
- Plumb MissionManager through MissionEditor
- Mission Editor supports get/set

- Only show video option if supported
- Persist settings
- Show/Hide/Add items correctly

While at it, fixed an issue with builds that have video streaming disabled.

- Restructured a number of MissionItem properties as well

When on Joystick config page:
- Not calibrating: If joystick is enabled, joystick messages should
continue to go to vehicle