grafx - Extensible Java Graphics Package Code

Making variables 'final' where I can, and now using the new
elevationAtGridLocation() function where I can. No logic/algorithm changes.

In EvalFunction, defining elevationAtGridLocation(), and using it in
overallHeightMetric() and in heightFluctuationMetric(). Meanwhile I found a
blaring problem in overallHeightMetric(), which had to do with the computation
for maxAltitudesPossible, which used the z-dimension twice instead of using
the y-dimension. This has been fixed, and the linear factor
OVERALL_HEIGHT_METRIC has been changed to compensate for the correction.

Nightmare level default, changed from index 4 to index 2.

This eval function does very well on the hardest level, level 23, even with the
adjustments made, causing it to have an extremely difficult block distribution.
I tested this and the computer player passed this level at least 5 times in a
row, with not a single failure, with these eval function settings.

Adding comment for plugTheHoleMetric(). This needs some very careful
consideration.

Beginning to work on plugTheHoleMetric().

Adding scripts/launch-hard-level-test.sh.

Adding missing println() for metrics.

Tweaking the linear combination of metrics. Performs well.

Fixing computation of meanAltitude in heightFluctuationMetric().