Computation of metrics to find interesting rulesets

[benpm]

Rule filtering: rules with less "noise" and more "persistent structure" should be automatically collected. The idea is something like scanning frequencies for a strong FM signal, but too much persistent structure is also boring. So here are the criteria:

1. Correlation between steps should be within a specific range
2. Oscillation should be ignored - treated as if the state did not change. We want rules like Game of Life
3. Motion should be rewarded - this could be done using something like HashLife - maybe the entire metric could be based off HashLife...