* src/glade-gtk.c: Simplified code with convenience functions

	* src/glade-editor.[ch]: Fixed visual state of labels in insensitive state.

	* src/glade-property.[ch]: Added glade_property_get/set_va_list

	* src/glade-widget.[ch]:
	   Added convenienve functions:
	    - glade_widget_property_get/set
	    - glade_widget_pack_property_get/set
	    - glade_widget_property_set_sensitive
	    - glade_widget_pack_property_set_sensitive