-add widget for edit it
-make link betwen QET -> QETproject -> Diagram, for transmit the xrefproperties
-xrefpropertie can save/load to xml and setting.
-XRefItem don't use the properties yet
git-svn-id: svn+ssh://svn.tuxfamily.org/svnroot/qet/qet/trunk@2983 bfdf4180-ca20-0410-9c96-a3a8aa849046
