Better handle the dirty state of Airmap's flightplan

Adjust fly overlay height
Change minimum Qt version to 5.11+

Restore QGC to its normal UI layout (buttons on toolbar)

Use consistent Altitude Mode labeling

Use new extraUnitField

Show extra unit in small font

Reduce space between graphic and text

Use standard Altitude Mode labeling

Add new file

Fix double tile download error reporting

Prevent double reporting of tile download errors

Offline Maps: Allow custom build settings overrides

Object ownership handled by SettingsGroup base class

Add support for ArduRover MockLink

Add FOLLOW flight mode

Heading: Switch from Radians to Degrees

Work around quirkiness with ArduPilot and LOITER_* NaN handling on heading.

No camera commands for ArduPilot