grafx - Extensible Java Graphics Package Code

Trying to fix lack of audio track in generated video.

Fixing spelling error for "${SCRIPT_DIR}/vid/ffmpeg-overlay.sh".

A first stab at copyright watermark using GIMP and ffmpeg-overlay.sh. Not
tested yet.

Adding Javadoc comment explaining naming convention of generated frames.

Adding img/transparent-image.sh script plus the needed new-image.scm GIMP file.

Defining scripts/.functions.sh. Moving some scripts to scripts/vid/ and others
to scripts/img/. Adding GIMP infrastructure. Simplifying existing scripts by
making use of .functions.sh. Renaming some scripts to dot files, e.g.
.generate-audio-track.sh.

Renaming LevelFinishedCausesNullNextBlock to FinNextBlockInterceptor because
this logic now also handles gameOver() states. It was needed to abstain from
calling the underlying nextBlockChanged() after gameOver(), because the game
logic will be calling BlockSource.getNextBlock() any number of times after
gameOver(), and when NextBlockSource is used, it also triggers a call to
nextBlockChanged(). We don't want that.

In SimpleGameLogic, on GAME_OVER also recording one next block after all other
events. This is causing problems right now, but I know how to fix and am
working on it. The problem is that the act of asking for the next block, for
purposes of recording to stream, is causing the next block display to be
changed automatically. Solution is to augment LevelFinishedCausesNullNextBlock
a little bit, perhaps even changing its name.

In SimpleGameLogic, taking a first stab at recording post-game events of type
NextBlockAfterFinEvent. Right now, recording one such event on level finished,
and not recording any on game over. Will test shortly.

Adding some TODO items to TODO.txt, before I forget about them.