* Giants to take 2-0 series lead to Detroit * Pence involved in both San Francisco runs (adds details) SAN FRANCISCO, Oct 25 - The San Francisco Giants moved a step closer to claiming a second title in three years by blanking the punchless Detroit Tigers 2-0 on Thursday to extend their World Series lead. 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 as the Giants opened a 2-0 advantage in the best-of-seven series. ...