More takeoff item fixes

Better wordings for Takeoff item

Fix for vehicle based home position management

Remove unused code

New user model for Takeoff item

Fix gradient calc

Fix incorrect usage of _settingsItem causing crashes

Group parameters with no metadata with the other existing params in the group, not in "Other"

Error display

Fix reference to settings from wrong thread

ADSB server support provided through new ADSBVehicleManager implemenation

More work on contextual Plan tools

Fix center drag and split side

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

RTL is no longer part of Mission Settings

Advanced tuning hidden due to crash from Qt problem

Fix takeoff item insertion in plan creators

Only show split indicator on mission layer

More work getting _addMissionSetting right

Reduce height of items in combo dropdown

Reword to use sizeToContents on combos for flight mode channels

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