Override Vertex Id Mapping

[tdashworth]

I see the following code in QuickGraph.Graphviz.GraphvizAlgorithm.Generate which defines the id used for each vertex:

int i = 0;
foreach (TVertex v in this.VisitedGraph.Vertices)
    this.vertexIds.Add(v, i++);

It would be nice to be able to override the default 1, 2, 3, n to maybe something defined in TVertex.