addEdge method
Add an Edge computed externally. The label on the Edge is assumed to be correct.
Implementation
void addEdge(Edge e) {
insertEdge(e);
List<Coordinate> coord = e.getCoordinates();
// insert the endpoint as a node, to mark that it is on the boundary
insertPoint(argIndex, coord[0], Location.BOUNDARY);
insertPoint(argIndex, coord[coord.length - 1], Location.BOUNDARY);
}