grafx - Extensible Java Graphics Package Code

Trying to clean up the Javadoc clutter in packages com.nerius.game &
com.nerius.game.util. I realized that in the release Javadoc there is too much
clutter, with too much information and too many classes that aren't needed
exposed in Javadoc.

Embellishing Javadoc in FrameAWTStub and taking care of some constructor
intricacies.

Making Javadoc for package com.nerius.game.util prettier. In particular,
BoardAWTAdapter no longer implements InputListener; instead it defines a method
getInputListenerHook() which replaces itself with a private inner class.

Removing the 'public' access modifier from class
com.nerius.game.util.DummyAudioClip; making adjustments in a couple of classes
because of this change. I want the Javadoc for all demo code belonging to
grafx and grafx_3d releases to look very clean.

Adding an explicit no-arg public constructor to DummyAudioClip.

Taking away the 'public' access modifier from DummyAudioClipSource. This class
is now package visible. This makes the Javadoc for grafx and grafx_3d demos
more understandable.

Removing an unused import statement.

Taking the 'public' access modifier away from class InputListenerChain; it is
now package visible.

Fixing some Javadoc issues in AbstractCanvas. Proofread all code in package
com.nerius.game; now moving on to another package to proofread.

These were minor changes made in grafx/ tree prior to releases of grafx
bundles; in particular grafx-2.0 & grafx_3d-1.0 were released on Nov 1st 2023.
Carrying these changes over to blockout/ tree. These are mostly Javadoc, but
include some use of 'final'. The Donut demo was updated significantly as well.