Sprite Decoder with More Format Support

As promised, the sprite decoder now interfaces with ImageMagick (Magick++) to read more palette formats and write more image formats.

Please be advised that using images as palette may cause precision loss, but this should not cause problems if you use tool to rematch the colors if needed (GIMP with imported palette and then Palette Tool match).

Do not use lossy formats if you intend to edit sprites!

Since this changeset.