[yjuanfzh] Graph layout to select edges

Given a graph in which nodes are connected by at most one edge, lay out the nodes on a plane, probably constraining them to be within a region, e.g., a unit circle.  Draw the edges as straight line segments between the nodes.  Mark the midpoint of each edge.  The midpoint represents a UI marker by which one can select the edge.

Find a layout which avoids midpoint markers from being close together.  Maximize the minimum distance between any pair.  Or electrostatic repulsion.

Add nodes into the mix if you want to select nodes or edges.

Motivation is a UI for the Strings And Coins game, the elegant generalization and graph theoretic dual of the Dots And Boxes game.

Pairs of nodes connected by more than one edge can have their edge multiplicity annotated on a single edge (at its midpoint).