Add dynamic graphs to frontend

[lehkost]

R package ndtv offers possibilities to render dynamic graphs, which we use to do exactly that, network data coming via our API. Here's Emilia Galotti as animated GIF:

We should add dynamic graphs to the web frontend as well, maybe by resorting to the ndtv-d3 library. Perhaps ndtv can also be combined with sigma.js.

(Our R code for this is on rpubs.)