Judith Dobrzynski reports on the Dulwich Picture Gallery's unique exhibition schedule for 2011: "one masterpiece every month of the year. It's like an unfolding calendar, it's like a year long advent calendar of your dreams." The schedule includes works by: Sir Thomas Lawrence, Velazquez, Vermeer, El Greco, Veronese, Rembrandt, Ingres, van Gogh, Gainsborough, Constable, David Hockney, and Domenichino. A year of must sees…