Support replay speed changing

Fix bug where QGCComboBox { model: ListModel would not work correctly

Add collision avoidance settings to Safety Panel

Update to the QGCComboBox to use a textRole in the case where it's availble.

Some small theme colour fixes.

Updating the items to be inline with the theme.

This is a small experiment into creating a custom theme for QGC.

Add gimbal to external control signal

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.

Move PreflightCheckList to custom builds only. The model, which used to be implemented within BuiltinPreFlightCheckModel is now within the control itself. It is up to the implementer to define a proper model.

Fix height

Fix typo

New qml base log replay status bar

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>