grafx - Extensible Java Graphics Package Code

Adding three new classes: FailedBlockInversionEvent, BlockInversionEvent, and
AttemptedBlockInversionEvent.

In BlockoutBoardEvent, defining BLOCK_INVERSION and FAILED_BLOCK_INVERSION
constants. Reformatting indentations in constant definitions, for clarity.
Taking 'protected' access away from constructor, making it package visible.

Clarifying comments in BlockTranslationEvent just a little bit.

Demoting constructor of AttemptedBlockTranslationEvent to be package visible,
no longer 'protected'.

Demoting constructor of AttemptedBlockRotationEvent to be package visible, no
longer 'protected'.

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.