More work getting _addMissionSetting right

Update unit test for no auto takeoff item add

Fix handling of _addMissionSettings

Tweak combobox visuals

Remove unused code

Support for new TakeoffMissionItem and Takeoff Tool 

Comment out noisy warning

Fix crash caused by clear method not resetting internals correctly

PolyLine -> Polyline

Warn about glide slope altitudes

Polygon/Line tool name changes

Fixed unused variable

Fix Create Plan vertical spacing problem

Integrate Create Plan overlay in File DropPanel

Add simulateClick support

SectionHeader no longer set width automatically

Dynamic sizing of message buttons

Delete icon and Command Picker ui

Separate progress bar handling for initial load, write and read batching

Fix display of param load errors

Revert QGuiApplication->QApplication change since it breaks message dialogs.

Check for pending param writes on app close

New centered PlanEditToolbar

Better incomplete data visuals

Rework Mission Complete dialog for correct Resume Mission on ArduPilkot

Hide pre-arm message when vehicle arms

Palette based coloring

Add missing flight modes