ADSB: Add transponder control for ping200x support

[nicholas-inocencio]

Codependent with ArduPilot/ardupilot#18637 and requires ArduPilot/mavlink#225.

Adds a Transponder tab with controls for the following ADS-B fields, for use with a ping200x.

• FlightID
• Squawk
• NIC
• NACp
• STBY/ON/ALT
• IDENT
  Additionally, adds indicators for the following:
• Maintenance required
• GPS Unavailable
• GPS No Fix
• Transponder System Failure
• On Ground

[AppVeyorBot]

✅ Build MissionPlanner 1.0.2901 completed (commit 4722a267be by @nicholas-inocencio)

[meee1]

Looks nice and clean. thanks!

[nicholas-inocencio]

I may have to amend some mavlink stuff here due to upstream changes to the uavionix.xml that I missed.

[AppVeyorBot]

✅ Build MissionPlanner 1.0.2916 completed (commit 2be7b8d208 by @nicholas-inocencio)

[meee1]

let me know when you think your done.. ill let it settle a little while before i merge

[nicholas-inocencio]

Will do.

[nicholas-inocencio]

I've finished making changes, assuming edits to ArduPilot/ardupilot#18637 and ArduPilot/mavlink#225 don't cause any changes on this end.

[magicrub]

@nicholas-inocencio looks like there's a merge conflict on here blocking it's merge. Can you take a look?

[nicholas-inocencio]

@magicrub Should be cleared now.

[AppVeyorBot]

✅ Build MissionPlanner 1.0.2982 completed (commit 84432d9e01 by @nicholas-inocencio)

[AppVeyorBot]

✅ Build MissionPlanner 1.0.2987 completed (commit 5ad6c703c7 by @nicholas-inocencio)