He's the most happy fella. Jack Ryan, 43, the North Shore investment banker, is running for the U.S. Senate on a platform of happiness and light. ''I just feel so much love in this room right now,'' Happy Jack declared at his campaign kickoff the other day at Hales Franciscan High School, where he gave up an investment banking career to teach a few courses. ''Every major religion says that happiness comes not from seeking our own fulfillment but from seeking the fulfillment of others,'' he said. ''We've got to start looking out for one another's happiness." Ryan, who has...