More work on contextual Plan tools

A contextual Land/RTL tool. Better waypoint line calc.

Only show split indicator on mission layer

Support for new TakeoffMissionItem and Takeoff Tool 

Fix Create Plan vertical spacing problem

Integrate Create Plan overlay in File DropPanel

Fix save state checks. Show overlay on New.

Wizard Mode for Create Plan

New Create Plan support

Fix centerViewport calculation

Fix SplitSegment insertion

Remove all case missing current index notification

Allow split of current segment

Add Terrain toggle to MapScale control

More work on direction arrows

Zoom buttons move to MapScale control

Toggle Rally Point insertion on/off.
Highlight current Rally Point and current Waypoint.
Use tab bar instead of a row of radio buttons for selection (Mission, Fence, Rally).
Fix QGCHoverButton to handle proper checked state toggle.
Get rid of the many arrays used to define behaviors for the ToolStrip. They are now all defined within its model.
Fixed color for disabled text within ToolStrip (it was invisible)

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.

Make ToolStrip font smaller (Desktop builds)
Check for auto configured video stream before testing video source type

Add support for geofence return point. Also fixed a bunch of bugs in geofence and rally point support.

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

Fixed flight widget position.

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

Waypoints only mode tweaks

Hide ROI

Visual cleanup