The image of Solomon Northup's body hanging from a tree -- noose around his neck, hands tied behind his back, feet barely touching the ground -- is uncomfortable to look at. And Steve McQueen, director of "12 Years a Slave," does not spare the audience with an expedient exit. ...................................................... The movie is an unsanitized portrait of a nation's shameful past. It is two hours of breathing in the antebellum South and then walking out of the theater trying to pretend the stench is all gone. There is no question that "12 Years a Slave" was the best picture of...