The title of general manager doesn’t completely capture the many tasks on Danielle Marmer’s to-do list in the two months since taking over the Professional Women’s Hockey League franchise in Boston. “It’s funny you should mention that,” Marmer said with a laugh. At 29, Marmer and her fellow GMs are on the ground floor of a newly established six-team league that will feature many of the world’s top players when it begins play in January.