Stable merge

Update OSX SDL2.Framework to 2.09

Mavlink protocol version negotiation fixes

Update SDL2.Framework to 2.09

Fix combo box height

Remove old code and fix typo

ArduCopter Heli: Support 8 servos

Replace usage of QMessageBox with a QML window.

Initial support for PX4 Rover

Moved the preflight checklist to a proper, modal dialog.

Fix height

Change Survey-In min accuracy

Support 8 servos

Change Survey-In min accuracy

Windows: Change USB driver detection logic

Change USB driver detection logic

Revert "Windows: Always install PX4 Drivers"

Firmware Flash: Fix crash caused by NULL vehicle

Instead of trying to keep a vehicle type within the FirmwarePlugin instance, pass the vehicle to the function so it can query the type that way.

Windows: Always install PX4 Drivers

Always install PX4 Drivers

Fix crash caused by NULL vehicle

Crash and typo fixes

Handle text to speech locale

Remove unnecessary AudioOutput dependencies.

Fix incorrect reference to vehicle causing crash