The House Of Silk By Anthony Horowitz Mulholland Books, $27.99, 294 pages, ISBN 978-0-316-19699-4 It's cold, foggy and snowy here in Colorado Springs.  In fact, it's sort of like London, England - where this week's MBR takes place.  It's a retro Sherlock Holmes mystery, the first one authorized by the estate of Sir Arthur Conan Doyle in it's one hundred-and-twenty-five-year history.  That fact alone tells us this one's so