This ensures no ports are being displayed to the user that are definitely unusable.

We were connecting to system peripherals before, which adds boot delay as QGC re-tries opening the port. We were also opening serial ports two times on Mac OS: Once as /dev/cu.usbmodem1 and once as /dev/tty.usbmodem1 - since the cu.usbmodem alias was already open, the 2nd opening always failed, leading to further boot delay.

These are now stored in json file

* 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

also moved back to flashing stable firmware for 3dr radio

Also enable identification of clone 3dr radios

Usability plus, new features:
- 3DR Radio support
- APM Stack support

- allow unit tests to use QGCApplication
- clear global singletons for each unit test run

Used for unit testing