feature request: Conversion from link communities output to node communities

[macks22]

Many evaluation scripts rely on communities of nodes, whereas clusterJaccards produces output files of edges. It would be useful to have a script that converts between the two.

[bagrow]

A script to go from non-overlapping link communities to overlapping node communities would be useful, but the other direction is generally not possible without losing information. Should be easy to write link2node; will look into it.