#2 create diagnostic output

[Jason Baldridge]

In the "eval" method of GISModel:

* Show the list of predicates contained in the String[]
"context". This could be expanded to show the list of
features and the outcomes to which each of them
contribute.

* iterate through the double[] "outsums" and print the
name of the outcome and the normalized probability
found by the model for it.

[Eric Friedman]

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Any thoughts on how this output should be reported? Shall I
test for the presence of a system property and, if it's
present and set to "true", write this information to
STDERR? My concern is that I'd like to make this change
have minimal impact on the "normal" performance of the
eval() method.