grafx - Extensible Java Graphics Package Code

After proofreading clearing up a couple of snafu's.

Introducing the zRot slide moves. It works. Will proofread shortly.

I don't think BlockPlacementStrategy will compile. I am saving changes in case
I want to go back to what I had.

Changing the rotateZ(Block) and rotateNegZ(Block) functions to be public.

Adding the rotateNegZ() methods.

Paving way for the analysis of possible post drop rotational slide moves. This
logic is really quite a bit more complicated than the previous logic which only
allowed a simple slide by one unit.

Now employing BlockPlacement inner class.

In BlockPlacementStrategy, defining inner class BlockPlacement, in order to
help with collision detection between well states that would cause eval() to be
re-computed.

Fixing the post drop slide issues.

The ComputerPlayer is now honoring all possible post drop movements, and these
have been somewhat tested. Right now it seems as if the AI only chooses slide
moves in the positive x direction, for some reason.