Thursday, December 23, 2004 'A Festivus for the rest of us' starts catching on By ALLEN SALKIN THE NEW YORK TIMES Gather around the Festivus pole and listen to a tale about a real holiday made fictional and then real again, a tale that touches on philosophy, King Lear, the pool at the Chateau Marmont hotel, a paper bag with a clock inside and, oh yes, a television show about nothing. The first surprise is that all over the country, many real people are holding parties celebrating Festivus, a holiday most believe was invented on an episode of "Seinfeld" first...