Using node links to make head cells
set linkDistance to fit with everything else
Properly colors and state implemented. Head is clumpy right now.
experimenting with multiple foci
got rid of links. only using foci now.
head nodes move to superhead now
Better colour differentiation; remove highlights button.
lofty goals
now able to toggle mouse highlighting
A->A,A and B->B,A working fully now.

If a node was a head node, it either becomes two head nodes (A->A,A) or
it becomes a head and a regular node (B->B,A).
spine working with manual iterate button