grafx - Extensible Java Graphics Package Code

Adding more examples for canPlugHoleWithoutPlacingCubeAbove().

Implemented canPlugHoleWithoutPlacingCubeAbove() in CoveredHoleMetric, but want
to proofread (and of course test eventually). Gave some examples in a comment.
Want to add at least one very complex example. Also in removed an irrelevant
comment.

Simplifying some indentation levels by removing 'else' blocks where possible.
CoveredHoleMetricUtils.java.

Starting to implement canPlugHoleWithoutPlacingCubeAbove() in
CoveredHoleMetric.

Finished the algorithm with the new x-ray technology. I need to proofread this
after a bit of rest. Completely untested. CoveredHoleMetricUtils.java.

Found a problem in the algorithm related to light rays vs. x-rays. Starting to
implement the fix. CoveredHoleMetricUtils.

Adding in the caching optimization. CoveredHoleMetricUtils won't check the
clearability of a single layer more than once.

Defining canClearLayerWithoutFillingCube() and helper
castRayOfLightUpwardsFromPositionInWell(). This code is complete, but
untested. It does compile. There are some optimization issues that still must
be implemented too. The discovery of this recursive function was a true
blessing. It was very difficult to discover, and took many days to pinpoint.

I'm stuck again, in CoveredHoleMetric. This is a very difficult problem.

Making huge progress on actually writing down code in CoveredHoleMetric.