#25 Bayes network module

[Jiri Baum]

Bayes net is a standard AI construct, which would be
particularly useful in diagnostic-like tasks (that is,
indicating causes based on sensor readings).

There may be standard packages to do Bayes nets, but I
don't know of any open-source ones.

Adding this feature would make our project more visible
to AI researchers, particularly those who work with
Bayes nets.