#26 use faster spring layout

[Rob Lintern]

spring layout currently runs in O(n^2) time

possibilities:
1. look at new implementation (possibly from Golbeck
and Mutton) that runs O(nlogn) or other ideas (graph
theory people?)
2. reduce the number of nodes on the screen via filters,
visualization/views on demand etc...too many nodes,
even if "sprung out," are messy