The couture parade is back in town — and I don’t mean the collection shows.  The 2007 Costume Institute Gala, celebrating the Paul Poiret exhibit at the Metropolitan Museum of Art, will take place on Monday, May 6 at the Metropolitan Opera House.  Those expected to walk the glamorous red carpet include Julianne Moore with Stefano Pilati, Jennifer Lopez, Cate Blanchett with Nicolas Ghesquiere, Mary Kate & Ashley Olsen with Giambatista Valli, as well as Jennifer Garner, Kirsten Dunst, ...