v0.2.3

Added

• rawstor-vhost@.service, a systemd template unit (packaged in librawstor) so callers can systemctl enable --now rawstor-vhost@<uuid> instead of supervising rawstor-vhost themselves. Derives its target from the instance name alone: ${RAWSTOR_LOCATION}/<uuid>.
• rawstor-ost now serves SPEC over the wire (new RAWSTOR_CMD_SPEC command); librawstor's ost:// client implements rawstor_object_spec() for real instead of returning an emulated fixed size.