Ripped Gen I Pokémon sprites. #245

The previous sprites were backwards, were too large, and had alignment
issues.  (Because they were made by cropping screenshots.)

This commit replaces the old, busted sprites with sprites ripped
directly from the ROM.  It also adds grayscale sprites.

Thanks to Peter O. (of UPC) and RHWiki for documenting the sprite
compression algorithm.

http://www.upokecenter.com/projects/rbgfx.c

http://www.magicstone.de/rhwiki/article/Grafikkomprimierung_PKMN_RGBY

Some notes:

- The media/jp-blue directory has been renamed to media/red-green.

- The grayscale sprites are found in the "gray" subdirectories.  For
  example, media/red-blue/back/gray/1.png.

- Frontsprites are 40x40, 48x48, and 56x56.  Backsprites are 32x32.
  The game blows backsprites up to 64x64 when it displays them.  The
  previous sprites were all 60x60.

- The sprite colors come from a Super Gameboy extension which allowed
  Gameboy games (which are normally grayscale) to display colors.

- The Red, Blue, and Green sprites have a pinkish, off-white background
  rather than a white one.  This is correct.  The background of the
  Yellow sprites is off-white too, but not as noticable.