Add some graphs to render network topology

From the data contained into wiremaps, it would be possible to get a network map. As a first step, it should be possible to use graphviz to get a basic graph for each protocol/information. As a second step, we could generate SVG which would be more like Visio. As a third step, we could allow the user to modify the SVG to place elements where he wants and Wiremaps would add links between them.
