Better wordings for Takeoff item

New user model for Takeoff item

Fix gradient calc

More work on contextual Plan tools

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

RTL is no longer part of Mission Settings

Fix takeoff item insertion in plan creators

Only show split indicator on mission layer

Support for new TakeoffMissionItem and Takeoff Tool 

PolyLine -> Polyline

Warn about glide slope altitudes

Polygon/Line tool name changes

Fix Create Plan vertical spacing problem

Integrate Create Plan overlay in File DropPanel

SectionHeader no longer set width automatically

Delete icon and Command Picker ui

New centered PlanEditToolbar

Better incomplete data visuals

Fix save state checks. Show overlay on New.

Wizard Mode for Create Plan

Fix incorrect import

Update for Qt 5.11

New Create Plan support

Start with no polygon

Bug fix

Corridor edit toolbar

Update for new controls usage

Survey items start with no polygon

Fix centerViewport calculation

Add Angle, Rotate, Stats to Presets page

Rework presets

Use TabBar in Complex Item UI

More work on mission item indicators

Fix SplitSegment insertion

Only hide generic waypoint indicators