IMPERIAL BEDROOM(LP)With his seventh album, IMPERIAL BEDROOM, Elvis Costello was hailed as being more than just a New Wave rocker. With intricate, Beatlesque arrangements and unusual, sophisticated song structures, Costello emerged as full blown master craftsman. Some of the more excitable critics of the day declared him a modern Cole Porter. Indeed, it's possible to imagine some 1940s torch singer crooning the slinky "The Long Honeymoon" or the mournful "Kid About It,"