SAN FRANCISCO, Oct 25 - The San Francisco Giants took a major step toward claiming their second title in three years by blanking the punchless Detroit Tigers 2-0 on Thursday to take a 2-0 lead in the World Series. Detroit was held to two hits by Giants starter Madison Bumgarner and relievers Santiago Casilla and Sergio Romo, failing to reach second base after the second inning. Hunter Pence was involved in both of the Giants' runs, racing home from third on a double play in the seventh inning and then lofting a sacrifice fly in the eighth to score Angel Pagan. ...