* src/glade-project-window.c:
	  o Manage the sensitivities of all the ui actions.
	  o Fix some issues with the Undo & Redo actions.

	* src/glade-project.[ch]:
	  o Detect if project file is read-only. New property "read-only"
	  o Detect if project has a selection. New property "has-selection"

	* src/glade-clipboard.[ch]:
	  o Detect if clipboard has selected items to paste.
	    New property "has-selection"

	* src/glade-utils.h: New function: glade_util_file_is_writeable ().