Unlock'd
Duke on 42nd Street, Prospect Theatre, Off Off Broadway By Eleanor J. Bader BOTTOM LINE: A madcap and entertaining, if somewhat hackneyed, look at gender roles and social class in 18th-century England told through poetry and song. Prospect Theater Company's production of the 2007 NY Musical Theatre Festival's "Best of Fest" Unlock'd " the show also received that year's Richard Rodgers award " tells a familia…