Make mugen1 "default" SP

[two4teezee]

Moves the WinMugen screenpack def and sff's into a winmugen folder, and brings the "mugen1" def and sff's into ./data.

Since we are using mugen1 to showcase new features, it would make the most sense for it to be in ./data and not the WinMugen assets.

[potsmugen]

I'm not sure if one of them is "more default" than the other. Maybe they could both be in subfolders since we don't own either of them for them to really feel default.

[two4teezee]

That makes sense. In that case I would agree with you - all of them in subfolders. It sounds like we use these mostly to showcase backwards compatibility, which is fine, but also a bit confusing.

That said, we should have a single reference implementation that we use to showcase all Ikemen features. This would be especially useful for folks developing game modes as modules. If we need to create something from scratch to which we have the proper rights, that is maybe something I can take on.