Basically autodetection of BTRFS based system depended on it being mounted as
root which is not a case in rescue system.

In schnapps it would be really handy to extract to snapshot we are about to
boot, not to the root.

Make cert-bakup behave differently if btrfs is found and use specific subvolume
for backup of certificates.

While the files are meant to be extracted during the factory reset, it
may be desired to extract a specific file at other occasion as well.
Provide the possibility.

Include 3-clause BSD licence headers to the tiny utilities.