Initial import of semi-working tetris.
Clear rows when they're done!
Cleanup.
Add support for all the basic pieces.
Render board last. Key repeat.
Initial work on "warp" mechanism.
Only render draggable if warping.
Functional dropping. Woo!
Warping mechanic improvements.

 - Don't show the game board when warping.
 - Only allow one warp per piece.
Comment and reorder pieces.
Mutate board when you warp. Bugfixes.
Dragging bugfixes.
Fix clearing bug.
Animate mutations of the board.
Move rendering and pixelmapping into BlockRenderer
Some cleanup.
Refactor a couple of variables.
Some more method refactoring.
Clean up nudging / landing checking.