Major rework to support terrain profile display and terrain collision reporting

Support for reusable InstrumentValueArea control

Set RC To Param support

QGCPopupDialog support

Integrate Create Plan overlay in File DropPanel

New Create Plan support

Corridor edit toolbar

New reusable file dialog for KML/SHP loading

Save/load main window state

Rework presets

Use TabBar in Complex Item UI

New QGCOptionsComboBox control

FW Landing slope heights display

New QGCDynamicObjectManager support

New base class control for Survey/Corridor

Add gimbal to external control signal

Move PreflightCheckList to custom builds only. The model, which used to be implemented within BuiltinPreFlightCheckModel is now within the control itself. It is up to the implementer to define a proper model.

New qml base log replay status bar

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

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

* QGCCheckListItem -> PreFlightCheckButton
* CheckList -> PreFlightCheckList

Automated preflight checklist: Initial commit. Note that this requires an autopilot firmware that writes the respective health flags in the SYS_STATUS mavlink message

Create a "Dead Mouse Area" control to eat mouse events underneath desired area. This is to prevent mouse events from leaking through controls underneath the area.
Replace original "NoMouseThroughRectangle" as this is more versatile.
Prevent mouse through events from leaking underneath the Fly View tool strip.

Moved "Grid Lines" out of General Options and into the Video Stream Widget
Made a QGC custom Switch element