grafx - Extensible Java Graphics Package Code

In AttemptedBlockMovementEvent, checking discrete values of 'axis' in
contructor, instead of checking range. We don't allow bitwise-ored values for
axis. Also adding no-arg constructor, which will probably be used for block
inversions. Adding short comment on the existing constructor.

In AttemptedBlockMovementEvent, removing usage of 'protected' modifier. That
would make the Javadoc more complex than it needs to be.

Fixing build with addition of invertBlock() where needed. Not implemented.

Adding UserInput.invertBlock(). This temporarily breaks the build.

Update on PIPELINE-NOTES.txt.

One more update to PIPELINE-NOTES.txt.

Adding to PIPELINE-NOTES.txt.

Adding PIPELINE-NOTES.txt.

Removing an old and unnecessary TODO file.

Renaming 'reflection.png' to 'mirror.png' because of Sourceforge caching issues
which have persisted for more than twelve hours on their website.