The idea of pro football games on Thanksgiving used to be a one-game affair, almost always featuring the Dallas Cowboys. The Cowboys indeed are playing today, but Dallas is only one of six teams showcased in three different NFL games televised nationally today. The first, broadcast by CBS at 12:30 p.m. ET, features the Chicago Bears vs. the Detroit Lions. The second game, on Fox beginning at 4:30 p.m. ET, has the Washington Redskins facing the aforementioned Cowboys. And on NBC’s Football