The annual convention of the National Association of Television Programming Executives, or NATPE, kicks off today and runs through Thursday. The Wall Street Journal's Sam Schechner files updates from Las Vegas. Monday, January 26 Las Vegas is cold. Pools are drained, hotels are sparsely filled, and rain is on the forecast. Inside, as the National Association of Television Programming Executives' yearly TV marketplace kicks off, the mood is scarcely any warmer: The TV world is girding for what's likely to be one of its most challenging years in decades. [Flavor Flav] Kevin Winter/Getty Images Hip-hop artist and reality-show star Flavor...