Hopefully this allows better finetuning and validating of what is possible in QML
for the various Qt versions.
In the long run we might want to qualify the class definitions with
QML_ELEMENT and friends to have better tool support ( qmlcachegen ??? )
See https://www.qt.io/blog/qml-type-registration-in-qt-5.15
all backgrounds ( color, padding ) without changing the overall fallback settings. This made
it possible to remove the confusing autoFillBackground property.
