systemd service: show doc URL

systemd service: show doc URL

ex.
netatalk.service - Netatalk AFP fileserver for Macintosh clients
          Loaded: loaded (/usr/lib/systemd/system/netatalk.service; disabled)
          Active: active (running) since Tue, 27 Nov 2012 01:03:44 +0900; 41s ago
            Docs: man:afp.conf(5)
                  man:netatalk(8)
                  man:afpd(8)
                  man:cnid_metad(8)
                  man:cnid_dbd(8)
                  http://netatalk.sourceforge.net/
         Process: 30813 ExecStart=/usr/local/sbin/netatalk (code=exited, status=0/SUCCESS)
          CGroup: name=systemd:/system/netatalk.service
                  ├ 30815 /usr/local/sbin/netatalk
                  ├ 30816 /usr/local/sbin/afpd -d -F /usr/local/etc/afp.conf
                  ├ 30817 /usr/local/sbin/cnid_metad -d -F /usr/local/etc/afp.conf
                  └ 30823 /usr/local/sbin/cnid_dbd -F /usr/local/etc/afp.conf -p /export/test -t 7 -l 5