music_ops.sh: add some ops for mp3 and don't consider these files junk.
.gitignore: delete, has no meaning to non-local configuration.
vnc: change menu key to Insert.

No Pause key on my new laptop.
boot_analyze.sh: allow overriding unit for critical-chain; add dot.
umount-iso: `umount -d` works incorrectly in some cases, don't use it.

HACK WORKAROUND: use `losetup -D` which will detach every unused loop device.
xplane: change base dir.