The nominations for television's biggest award, the Emmy, were released on Thursday morning, adding more fuel to the argument that much of the best creative work in the medium is now being done on cable, and to the perception that shows do not necessarily need big audiences to be celebrated by the television academy. That point was underscored by the emergence of the little-watched (but much written about) series ''Mad Men'' on the cable channel AMC, which received nominations in the categories... ...