Plan: More work on contextual Plan tools

QGCMapPolygon: Fix center drag and split side

More work on contextual Plan tools

APMHeliComponent - update for Copter 4.0

Plan: Land tool

Advanced tuning hidden due to crash from Qt problem

Fix center drag and split side

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

RTL is no longer part of Mission Settings

Update for non bug reports

Update

Plan creator: Fix insertion of takeoff item

Advanced tuning hidden due to crash from Qt problem

ParameterManager, ParameterEditorController: Nice category & groups for components

Fix takeoff item insertion in plan creators

Only show split indicator on mission layer

Reduce height of items in combo dropdown

PX4 Flight Mode: Rework to use sizeToContents on combos for flight mode channels

Plan: Takeoff tool and Takeoff item support

More work getting _addMissionSetting right

Reduce height of items in combo dropdown

Reword to use sizeToContents on combos for flight mode channels

Tweak combobox visuals

Remove unused code

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

Simplify mission item list 2