Kate Moss, wearing a crystal dress with an open back that exposed a G-string with a bejeweled logo, a tribute to Tom Ford, surprisingly closed Demna's first show as creative director of Gucci Friday.     For the occasion, Milan's Palazzo delle Scintille, transformed into an imaginary art gallery complete with ancient statues, hosted guests including former creative director Alessandro Michele, seated next to Donatella Versace, and Hollywood star Demi Moore.     "There are a lot of people who