Sailors labor on gliding high rises.  Freighters are run by fewer than two dozen people.  They may stop at half a hundred ports and never go ashore.  For them, Boston harbor is some place special.  Wally Cedarling lives here.  He is a minister who has no church.  Each ship is his congregation.  In the few short hours between the tides, he wanders the decks offering a touch of home.