New XYX demo

New demo (3 levels), bringing it up-to-date with features in the current (full) version such as 2P, TATE, key config, etc.

This also includes an unfinished version of the Level/Map Editor. I've chopped some stuff out to make it better match the demo content; but nothing that effects it's functionality. I'll probably put together some more detailed docs later; but here's a brief rundown on how to use it.

Within the editor:
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MAP - This is strictly for assembling the graphic map for the level. Note that these will automatically loop. Also note that I've only tried fairly small maps so far.

LEVEL - Define enemy layout, checkpoints and hinge points (based on in-game step #), music, and background layer(s.)



Separate stuff:
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Music
-custom songs go in /custom/songs and must be in .ogg format (SuperSound limitation.)
- in levelbuild.txt, under [songs]:
-- fn#= (file name w/o directory)
-- tt#= (song title)
-- au#=(song author)

Gfx
-custom gfx go in /custom/gfx
-  files must be in recognizable formats (any that GM will accept) and the image dimensions must match those of the sample images (160x54 I think)

- in custom_mapset.txt, under [titles]:
-- #= (custom gfx set name)
-- each added set should be given it's own section below this in [] brackets with the exact same name as that indicated under [titles] Underneath it should go...
---image#=(file name w/o directory)
---imagetrans?#=1 (for the corresponding image number, if you want that image to have a transparent color. The particular color is based on the bottom left pixel.)