The "-->choose Material" has been replaced with a not defined material.
That makes setting/retrieving material to/from the object much easier
and allows user to have a "not defined" material. Previously it wasn't
possible to change i.e. form Steel to "not defined".
Signed-off-by: Przemo Firszt <przemo@firszt.eu>
Materal editor is now funcional, abeit not complete. Can be used to
create and save new cards. Lauch from within FreeCAD with
import MaterialEditor; MaterialEditor.openEditor()
