WASHINGTON — Eric Holder talks about the nation’s civil rights struggles in a way no previous U.S. attorney general could — by telling his own family story. As he increasingly pushes his Justice Department to protect voting rights and end unfair prison sentences and police brutality, Holder has drawn on personal history to make the case that the nation has much work to do to achieve justice for all. It’s a legacy he’ll likely draw on when he travels today to Ferguson, Mo., to supervise …