grafx - Extensible Java Graphics Package Code

Getting rid of 'level' field in GameSidebar. Making adjustments with
NextBlockDisplay, in its placement and size.

Adding a 7-er test level.

Removing level23-game.blo & 7-er-blocks-all.png.

Re-generated Blocks.java with the recent changes, which expose 7-er blocks.

The file which generates Blocks.java, namely GenerateBlocks.java, not exposes
an ability to get 7-er blocks.

Adding "throws IllegalArgumentException" clause for more clarity.

Adding BlockGifImage which generates an arbirary block image from string.

Adding BlockGenerator.getBlockFromName(). Not tested yet.

Fixing compile error.

Improving this PNG file.