QGCFileDialog remove separate mobile fileExtension properties

Propagate opacity and interactive properties to mission items
Set opacity to 0.5 for items that are not part of the current
edit view

Fix Done Tracing <-> Done PolyFoo in wizard relationship

PolyLine -> Polyline

Polygon/Line tool name changes

New centered PlanEditToolbar

New Create Plan support

Button name changes

Corridor edit toolbar

Use new SplitIndicator control

Make visibility work

Update all files that use a QML Menu item to QtQuick.Controls 2.4 to solve the issue of a menu showing up in random places on Android.

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