ListView: Generate C++ classes from data structs

[skaldesh]

Check out this guide: https://doc.qt.io/qt-5/qtquick-modelviewsdata-cppmodels.html

Maybe we can stop sending QVariants over the go-qml bridge, and use proper C++ classes. This would greatly simplify the access to the list elements in QML (compare "display/model.display" with JSON.parse against simple "text" or "name" accesses).

This would need something like a gml.ListViewData class that is added to the data struct in go