Harbaugh coy about identity of emergency quarterback

Plenty of NFL teams carry only two quarterbacks on the 53-man roster.  Through two-plus years in the league, 49ers coach Jim Harbaugh hadn’t been one of them. But with receiver Michael Crabtree back, a roster spot was needed.  Harbaugh sacrificed his No. 3 quarterback, McCleod Bethel-Thompson. So with Bethel-Thompson now on the practice squad and…