Cleaned up Board.java. Still need to test, but passed initial sanity-check testing.
Added PDTrials to run multiple trials for a set of initial conditions.
The system appears to be chaotic enough, at least for small boards that this is
necessary.
PDTrials tests boards filled with uniformly random certainty values, uniformly
random + some deviants with large certainty values, uniformly random + some
deviants with small certainty values, and uniformly random with some deviants
with smaller or larger certainty values.