if you compile and go to graph, navigator will crash.
This is probably due with the call of dispatch(d) in Graph.purs.
Work perfectly fine with log instead of dispatch.

Revolved last bug, i was writing in the wrong renderer (we really need to
factorise this code)

Problem with type for myGoto

Done using DisplayEdge action. We can now toggle the edge drawing using the
button "Toggle Edges" in the toolbar.