Migrate `Gtk::ListStore::iterator` code

[taozuhong]

Here are two examples for you:
taozuhong/GtkColumnViewDemo: A GtkColumnView demo app (github.com)

GListModel support modified items?

The GtkExpression and GObject::notify can’t cover the computed or multiple value scenes, for example: The Row object has many items (column value object), one of them changed its hold value or property, maybe multiple values at time. In our case, we make many changes at time, then refresh the UI (GtkListView / GtkColumnView) normally, pls see the Vala code as follow: public class ValueObject : Object, IValue { public virtual string name { get { return "UNKNOWN"; } } public…