Z7_STRING handling in the function cells_for_geo_points

[tik65536]

The function cells_for_geo_points needs to be adjusted to handle Z7_STRING from line 1415 onward.

   if cell_ids_only == True:
       # The column name should align with output_address_type 
       geodf_points_wgs84['seqnums'] = cell_id_list
       return geodf_points_wgs84
   else:
       # grid_gen from seqnums
       #  Here need to add the input_address_type and output_address_type to align with what is pass in
       gdf = self.grid_cell_polygons_from_cellids(cell_id_list=cell_id_list,
                                                    dggs_type=dggs_type,
                                                    resolution=resolution,
                                                    mixed_aperture_level=mixed_aperture_level)

Tik