By Denny Dyroff, Entertainment Editor, The Times  Reindeer arrive later in the week but cats get here first. On December 20, the Greater Philadelphia Expo Center (100 Station Ave., Oaks, 484-754-3976, http://www.phillyexpocenter.com) is hosting the “Loving Cats Worldwide® Catstravaganza: Philadelphia,” which is billed as “the show for people obsessed with cats!” The feline-based experience...