Idea: organize file type detectors

[Wohlstand]

For a better organizing, it's would be cool to move any format detectors into music_*.c as a helper function to make the file type detection process be more organized?

I mean something to like here:
https://github.com/Wohlstand/OPL3BankEditor/tree/master/src/FileFormats

• every file format definition has a "detect()" call that tries to test a file is it's this format on aboard or not: https://github.com/Wohlstand/OPL3BankEditor/blob/master/src/FileFormats/ffmt_base.h#L35
• once format was confirmed "it's mine!", then, this format class is taking for a processing

This will improve scalability and allows easier adding of new file formats without of extra "music.c" hacking (to add more type detection codes into specific calls).