Force tree transition chaining (incrementally showing nodes and links in a force graph); single nodes appear incrementally

Force graph with node-link show up through chaining …… ? 8

Derived from gist 1125997 and gist 2511921, but now shows the nodes appear incrementally.

This variant also chains the display of the links one by one; links are only shown once their nodes are visible.

The alternative, which fades in all relevant links all at once for each node which shows up, see gist 2511921.