* src/glade-project-window.c:
          o integrate ui into one main window.
          o A GtkNotebook is used to display GladeDesignView's.

        * src/glade-project-view.[ch]: add "item-activated" signal.

        * src/glade-design-layout.[ch], src/glade-design-view.[ch]:
          new files.

        * src/glade-widget.[ch]:
          o Added functions for embedding toplevel GladeWidgets
          o glade_widget_show() modified to manage embedding of
            toplevels.