Make lengths between nodes in P-metanodes bigger

[fedarko]

The "compressed" nature of P-nodes makes a few things difficult:

• Right-clicking on P-nodes to collapse/uncollapse them in the explicit SPQR mode
• Visually understanding what's going on (sometimes, the edges in the P-node get clustered together since the distances between the two nodes are so small -- also, occasionally a few of the edges won't even be initially rendered by Cytoscape.js because they're so compressed, and I don't think this is resolvable using the "convert to bezier" approach since they're already beziers)

See if we can use len and weight or something for edges in P-nodes? Might have to set sfdp's mode to "maxent" in order to get it to recognize edges' requested len attributes.

[fedarko]

So after a few hours of messing around with nodesep, sep, len, weight, fdp vs. neato vs. sfdp, K, splines=true, ... I still haven't made much progress on this.

However, I think I figured out a way to do this without GraphViz. When laying out the interior of a P-metanode, find the node with the maximum x position (there are only two nodes inside a P-metanode so this shouldn't be that hard to do) and shift it over by some amount (experiment to figure out what looks good—maybe 1 inch or so?). Shift over the x-dimension of the bounding box of the metanode by the same amount. I think this should have the same effect that I was going for here.