Greed, corruption, exploitation, murder and, of course, some good, old-fashioned razzle dazzle. Opening tonight at the Sacramento Community Theater to a sold-out audience, "Chicago" shows that all the world is a con game and the stage is the biggest scam of them all.   Set in the decadent 1920s, "Chicago" tells the story of Roxie Hart, a bored, philandering housewife, who dreams of one day seeing her name in lights and murders her lover when he decides to walk out on her. Gut-bustlingly playe... erinhaight