Plus lots of other cleanup

- MultiVehicleManager is a Qml friendly replacement for UASManager
- Vehicle is a replacement for both UAS and AutoPilotPlugin

also adds AMSL output in ft

Most math and backend storage was floats anyways, so most of these changes just half the data copied during function calls without reducing precision.

This fixes a bunch of bugs with setting the title for widgets, deleting
widgets, etc.  It also reduces the amount of code duplication, which is
always a good thing.

Removing UASes now returns the UI to an almost pristine state. This was done by altering the activeUASSet signal so that it can emit a NULL UAS. Crashes may still exist in autopilot-specific code.

Partway through refactoring of UAS deletion. This is in order to actually support removing UASes from QGC, which is currently impossible.

Removing UASes now returns the UI to an almost pristine state. This was done by altering the activeUASSet signal so that it can emit a NULL UAS. Crashes may still exist in autopilot-specific code.

Partway through refactoring of UAS deletion. This is in order to actually support removing UASes from QGC, which is currently impossible.

Impl. Lorenz suggestions wrt one velocityChanged, altitudeChanged, speedChanged signal per reference frame. Impl. CDI on compass disk.

Synchronized the dark theme to the changes to the light theme from the last commit. Also made more text change color based on selected theme.

HIL config improvements, fixed confusion about which dock widget is part of which view, main window behaving now

Fix for layout glitch when using HIL Configuration, and added checks to see if there is an active UAS before attempting to connect HSIDisplay signals