- Add initial definition of Config object, which will extract the model-
setting and loading code from the page, and which is also prep-work
for a QML version of this module.
- While here, remove superfluous code
- Just some simple tests for the Items
- Test creation of package group from variant
- This needs Qt5::Gui to link because QStandardItem is a GUI class,
although we can run the tests without a GUI.
