* lisp/play/tetris.el: Cleanup image representation and rotation.

* lisp/play/tetris.el: Cleanup image representation and rotation.
(tetris-tty-colors, tetris-x-colors, tetris-blank):
Remove leading nil element, adjust values.
(tetris-shapes, tetris-shape-scores):
Change representation of shapes and remove some redundancy.
(tetris-get-shape-cell, tetris-shape-width, tetris-draw-next-shape)
(tetris-draw-shape, tetris-erase-shape, tetris-test-shape):
Adjust for working with new representation of shapes.
(tetris-shape-rotations): New function.
(tetris-move-bottom, tetris-move-left, tetris-move-right)
(tetris-rotate-prev, tetris-rotate-next):
Adjust for working with the new version of tetris-test-shape.