ProjectDemo: store document names in persistent root metadata, rather than inner objects. This makes the name behave better wrt copying documents, step forward/backwards

git-svn-id: http://svn.gna.org/svn/etoile/trunk/Etoile/Frameworks/CoreObject@10188 7b3f36aa-e6db-49c1-8b4c-66eac1997e64