stage2 requires extracted root

[Ryan Finnie]

stage2 requires an extracted root for looking for a few things like /etc/finnix-version. For simple overlay/RC remastering, this should not be necessary. stage2 should be able to function without an extracted root, using another source for the version number.

Also, extracted root is required for grabbing modules during an initrd rebuild, which itself is optional.

(The wiki docs state that extracting the root is not necessary for overlay/RC remastering, so either the docs are incorrect or this is a bug. I'd rather this be a bug.)

[Ryan Finnie (fo0bar)]

Added checks for /etc/lsb-release either in $MASTER to $INITRD. If neither are found, $STUFF/lsb-release is used. If that is not found, the user is instructed to copy /etc/lsb-release from the running Finnix system into $STUFF/lsb-release.