Force tronweb action graph to be (more) visually topologically sorted

[striglia]

For sufficiently complex action graphs (soon to be made more complex by #614), the visualization's habit of just centering on a node and letting the rest fly free produces a very challenging visual.

I think my ideal visual is something closer to a topological sort where the root of the action graph is anchored somewhere (top is my default) and then we push each layer in the graph down to another row (or probably equivalently, left to right horizontally) to keep them better separated and make the DAG's directionality more obvious.

[solarkennedy]

Related to #747