grafx - Extensible Java Graphics Package Code

In launch-nightmare-mode-test.sh, adding ability to specify level.

Removing unnecessary import statement, embellishing comments.

Adding NightmareLevels.java. Can't decide between 'NightmareLevels' and
'NightmareModeLevels'.

Adding a couple of played games, by computer player.

Starting to add copyright notices to shell scripts. Making
launch-computer-player-test.sh have ability to choose level without script
modification.

Adding a new level, 6x5 pit w/ 6-er blocks.

Fine-tuning qSearchBreadth, qEpsilon, and nEpsilon. In particular I put
emphasis on choosing a move that is appealing as far as only the current block
is concerned. This is why nEpsilon is low (0.0001) and this is why qEpsilon is
higher (0.0004). The future possibilities that we consider are not as
important as is the placement of immediate block, in my opinion. This sort of
conundrum has been causing problems in the past.

Improving comments in BlockPlacementStrategy.java.

The computer player was being a little bit too greedy in jumping to
opportunities for clearing layers.
Changing OVERALL_HEIGHT_METRIC from 0.50 to 0.45.
Changing SQUARED_HEIGHT_METRIC from 0.15 to 0.12.

Dividing epsilon into qEpsilon and nEpsilon.