UI fix: Removed 'label' text from one label, it was displayed durring startup
Little cleanup in app.glade, removed few warnings
Fix: Sensitivity of traditional header menu button
Added option to toggle menu icons in UI Settings (ignored on Gnome); Re-enabled Window menu button relief in Windows; Set appmenu to be used only with Gnome
Do not show Header bar and menu icon configuration under Gnome (and Unity)