Feature: prevent self-referential edges

[marco-santini]

Hi, svelvet 7 is awesome. It would be nice if you could prevent self-referential edges on the anchors of the same node es. A-2/N-1 --> A-1/N-1

[briangregoryholmes]

We can add a flag for this. It may make sense for this to be the default behavior, with a flag to turn self connection on.

[marco-santini]

That would be great