##

     Browser function

     In the modes VWR and CAD the browser window is left of the graphics window
      - All objects of the model are presented here;
      - Selecting an object, (like in the graphics window, using right/outer mouse button) displays an object-specific menu.

      Appearance:

      The first node is the main model
      all internal sub-models are presented below this.

      Under the model name groups of objects in the model are
      shown. Using the right/outer mouse button the object groups can
      be opened and then closed again.