Add support to circuit visualization using JUNG (or other)

[vitorenesduarte]

Almost there with 674120e9b776e1ff8da0bddad02eda0849375885 and b42ea1d82b20b3fbe0cc05c37c10519cf3f8ca1b.

Missing:

• see if it's possible to define vertices' position in the view.

This will allow better visualization.

[vitorenesduarte]

Position solved with adcf9d3cf87f57539b4b502e6708acb26ebd6cdb.

Still not perfect. Possibilies:

• better algorithm
• find a new lib that provides automatic positioning of vertices

Closing for now.