Stuffing bootstrapping of archive-keys for derivatives into lb_config, it's not a runtime thing and its logic should not be embedded in live-build but the config directory.

Replacing os.link calls for hooks with shutil.copy to properly dereference symlinks in python stubs.

Updating rsvg calls in binary_syslinux for newer versions of librsvg2-bin, thanks to Roberto Carlos Morano <rcmorano@emergya.com> (Closes: #728030).