(Adds details, quotes) Oct 17 - The St Louis Cardinals, powered by back-up player Matt Carpenter, beat the San Francisco Giants 3-1 in a rain-delayed Game Three on Wednesday to seize a 2-1 lead in the best-of-seven National League Championship Series. Carpenter, who replaced injured outfielder Carlos Beltran, cracked a two-run home run in the third off Giants starter Matt Cain to give St. Louis a 2-1 lead and send the Cardinals on their way. ...