DAVIS MUSICAL THEATRE CO. An ambivalent Cinderella? A blood-thirsty Little Red Riding hood? A Prince Charming with a roving eye? They're all among the cockeyed characters in James Lapine and Stephen Sondheim's fractured fairy tale centered around a childless baker and his wife whose only wish is to lift the family curse and live happily ever after.  Thus, what begins as a lively irreverent fantasy becomes a moving lesson about community responsibility and the stories we tell our children. Fri & Sat, 7:30p; Sun 2p. $20