PluggableRendererDemo known issues

[jrtom]

The following items don't work:

• [ ] vertex stretching
• [ ] displaying voltages (values seem incorrect)
• [ ] filter when degree < 4 includes a node with what looks like a single self-loop
  • but maybe this is the parallel edge thing being busted again
• [ ] enabling/disabling vertex size by voltage
• [ ] changing edge shape
• [ ] edge gradients (aren’t the edges undirected?)