add slave element class.
element class: replace diagramcontext informations by elementInformations because informations is already used in xml file for element.
minor improvement.
git-svn-id: svn+ssh://svn.tuxfamily.org/svnroot/qet/qet/trunk@2869 bfdf4180-ca20-0410-9c96-a3a8aa849046
Add widget to edit it, save/load works
Informations are stored in a diagramcontext, this class was modified (new feature) to store information
but keep compatibilty with older version.
git-svn-id: svn+ssh://svn.tuxfamily.org/svnroot/qet/qet/trunk@2850 bfdf4180-ca20-0410-9c96-a3a8aa849046
