code: public Box box(double south, double west, double north, double east) {
      return new BoxImpl(south, west, north, east);
    }
docs: Specifies a geospatial region as a box, supplying
  the coordinates for the perimeter.
  @param south    the latitude of the south coordinate
  @param west    the longitude of the west coordinate
  @param north    the latitude of the north coordinate
  @param east    the longitude of the east coordinate
  @return    the definition of the box