Promote save_disk to an FS-UAE option?

[FrodeSolheim]

This option is currently only understood by FS-UAE Launcher. When checking the box in the Launcher, the Launcher adds a blank save disk to FS-UAE's floppy swap list.

But, it is possible to make it an FS-UAE feature, where FS-UAE itself can create and add the disk. If so, also probably make it possible to preformat the disk with a specific volume name, e.g.

save_disk = DSAVE

for It Came from the Desert.

[FrodeSolheim]

http://eab.abime.net/showthread.php?t=85412