New England business revenues are on the upswing, but an uncertain economic and political outlook has stopped many employers from hiring, according to a survey released by the Federal Reserve. “With the exception of software and [Information Technology] services, contacts say their firms are doing mostly replacement hiring,’’ the survey found. Known as the Beige Book, the survey is published eight times a year in advance of the Fed’s interest rate setting meetings. Fed policy makers meet Dec. 13.