grafx - Extensible Java Graphics Package Code

This Spiral.java code seems to work correctly at least in many of the cases.
Well now it's time to make sure that it's correct in all cases, and it's time
to simplify it.

Adding a comment to BlockPlacementStrategy which dicusses order of the spiral
iteration of xOff/yOff. This is nothing but a comment at this point.

Adding temporary file 'Spiral.java' which does not fall under any package.
This is my temporary scatch pad to figure out how to make the proper xOff/yOff
iteration in BlockPlacementStrategy, which starts from somewhere near the
middle and expands outwards. This is trickier than I originally thought, and
so I'm saving this work under source control, until it's perfect, at which
point it will be moved into BlockPlacementStrategy.

Increasing qSearchBreadth from 20 to 24.

Adding a comment on level 27.

Streamlining the clearing of layers in BlockPlacementStrategy. This should
speed up the decision-making for best move even more.

Caching the return value of getBestCanonicalRotation().

Now that BlockPlacementStrategy has been optimized and now that it runs more
quickly, increasing qSearchBreadth in ComputerPlayerLevelAction from 16 to 20.

Making level 29 a wee bit harder.

All comment and error message changes, in BlockPlacementStrategy. The
proofreading with a fine-toothed comb is nearing an end. I will likely test
extensively with various levels, but I also want to redo the order in which
xOff and yOff are set, to start from center and move towards outside.