grafx - Extensible Java Graphics Package Code

Removing two unused import statements from LevelPlayback.

Modifying LevelPlayback to incorporate the now external class StatsUpdater.
Changing names of some member variables in StatsUpdater. These changes seem to
be very worthwhile, because this same logic is being used in about four
different places.

Calling the setXXX() methods on underlying CubeStats object at construction
time of StatsUpdater, so that these would not have to be called in every place
where StatsUpdater is used.

Rearranging a few minor details in StatsUpdater. It all seems to be correct.

Adding external class StatsUpdater, but it isn't being used yet. I should
proofread this code again. Not even tested yet.

Adding interfaces CubeStats, LevelStats, & NightmareStats, and having
GameSidebar implement them.

Modifying NightmareLevelTest to use external ScoreReporter class.

Updating ComputerPlayerTest to use external class ScoreReporter.

In LevelTest, using ScoreReporter that is in a separate class file now.

Speeding the block moves back up from 210 millis to 200. It was too slow.