Custom, single firmware upgrades were fixed to "stable", even if the user selected "custom".
The code, when selecting the firmware type was using the combo box model index instead of the actual type defined by the list model.

Radio upgrade: Point updater to a binary which is fully MAVLink 2.0 enabled, including radio status.

This adds support for the full-sized FMUv4PRO design and the FMUv5 STM32F7 based generation.

* Fix minor spelling error

* Added support for the AUAV x2.1 Flight Controller
    also removed a duplicate entry for MindPX
    from src/comm/USBBoardInfo.json

Adds entries required to correctly identify, download and flash PX4
firmware to the AUAV X2.1 Flight Controller

* Update USBBoardInfo.json

Removed un-needed fallback entries. This has been tested!

* Add support for another board

* Added a 2nd custom board

3DR Radios no longer exist

Domain changes for the ArduPilot locations from DIYDrones to
ArduPilot.org

I removed some needed headers from a top level file which then causes a
ripple effect downstream

Removed commented v4 ArduPilot Quad fw links

To address issue https://github.com/mavlink/qgroundcontrol/issues/2735

- Also fix vehicle selector dropdown in toolbar