grafx - Extensible Java Graphics Package Code

The third in the series of changes, please see previous comment. Allowing
FFmpeg modifier to be passed to source video, sub video, overlay image, and
output video.

Second in a series of changes, please see previous log comment. This commit
may have some slight problems with the 'cut' command esp. when using
'--complement', which will be corrected in the next commit.

Making a series of three or four changes to scripts/vid/ffmpeg-overlay.sh which
will allow custom FFmpeg flags to be set on source videos (including base
video) and on output video. For example, scaling will be possible on all
source videos and images, and on the final output video. Much more will be
possible as well. This change simply introduces the '[N:v]null[videoN]' chain
terminology to overlay images (where 'N' is a number starting from zero) to
overlay images. This was already present in overlay video and on the base
video. The 'null' inside of this term will then be possibly modified with
scale properties etc.

Adding newer ffmpeg-overlay.sh script which has finer control of audio. Making
use of it in .compile-video-base.sh. Changing default level in
launch-computer-ai.sh. Adding 'set -e' flag in
combine-video-audio-shortest.sh.

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.