Apply a Gaussian filter to a grey-level woolz object
      writing the new object to standard output
      Options are:
      -w#[,#] x_width[y_width] gaussian widths defined as
            full width half maximum in pixels
            default value 3.0, if y_width omitted
            then it is set equal to x_width
      -x#       x derivative - possible values 0,1,2, default - 0
      -y#       y derivative - possible values 0,1,2, default - 0
      -h       Help - prints this usage message