Method move

src/svgfill/src/graph_2d.h:161–173

    void move(const Point_2& from, const Point_2& to) {
        // @todo should check for intersections?
        auto it = adjacency_list.find(from);
        if (it != adjacency_list.end()) {
            auto neighbours = it->second;
            for (auto& n : neighbours) {
                adjacency_list[n].erase(from);
                adjacency_list[n].insert(to);
            }
            adjacency_list.erase(it);
            adjacency_list.insert({ to, neighbours });
        }
    }

    bool is_valid() const {
        typedef CGAL::Box_intersection_d::Box_with_handle_d<double, 2, size_t, CGAL::Box_intersection_d::ID_EXPLICIT> Box;