Clean up references to MainRootWindow globals

Rework Fly View into separate layers which can be customized at each layer.

- Reimplement same behaviour as version 3.1 while resizing the window :
    Stretch the text area to fit the screen
- Change setting text from Alternate Instrument Panel to Vertical Instrument Panel

The instrument widget layout is now a stack of :
- QGCAttitudeWidget
- Item that contain ValuesWidget
- QGCCompassWidget

Get rid of QGCView, QGCViewPanel and FactPanel. All messages and dialogs are now handled in the root window.

Prevent clicks going through top level items

Eliminated flight widget "states"
Define flight widget top margin (plugin options)

Clarify the title of the "Video Stream" panel (instead of just "Video")

Fix active binding

Android done.

Plumb through initial object mode on Vehicle