* make Drag/DropArea overflow on the attribute's label to be more tolerant when connecting attributes
* add visual feedback when hovering interactive areas
* tweak spacings between attributes
* fix ListAttribute => ListAttribute with children (was breaking multiple simple connections to a ListAttribute)
* add missing case ListAttribute => Attribute
* bugfix: in latest PySide2 versions, application palette is not properly applied to all QtQuick Controls 2 components. Force this by exposing QApplication palette and bind it to the root ApplicationWindow.
* rename all "palette" ids to "activePalette" to avoid clashes with "palette" property on QtQuick Controls 2
* use parent component palette when it makes sense to propagate active/disabled style (instead of always using Active SystemPalette)
