Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.
I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
This adds a generator and a small service that will look for "roothash="
on the kernel command line and use it for setting up a very partition
for the root device.
This provides similar functionality to nspawn's existing --roothash=
switch.
