GGU-3D-SSFLOW: "Import/export" menu item

The x- and y-coordinates of the interpolation mesh can be imported from an ASCII file or exported for other applications. A dialog box as described in Section  "Import ASCII file menu item” opens for the "Import ASCII" option.

If the coordinates are exported using the GGU-3D-SSFLOW format, the information regarding triangles (incidence table) and z values will also be exported and can be imported again.