ProjectDemo/Sketch: store origin and size in separate properties, so we can selective undo changes to position and size independently. This is kind of a gimmick for demoing :-)

git-svn-id: svn://svn.gna.org/svn/etoile/trunk/Etoile/Frameworks/CoreObject@9810 7b3f36aa-e6db-49c1-8b4c-66eac1997e64