 * Use Compact when possible, like no signals (see http://live.gnome.org/Vala/ReferenceHandling)
 * Try to replace multiple GObject in App by a data memeber :
    public enum AppType {
        WM,
        PANEL,
        DESKTOP
        }
    public class App {
        private AppType type;
    }
 * Implement stages from GNOME
 * Investigate the removal of LibGee
