In this July 3, 1963 file photo, U.S. President John F. Kennedy stands at the lectern behind a production slate board during a television taping at the White House. (AP Photo) by Frazier Moore AP Television Writer NEW YORK (AP) — It’s a measure of how long ago President John F. Kennedy died that, at the time, television was described as a young medium. With the shooting in Dallas, TV grew up. Coverage that November weekend 50 years ago signaled, at last, that television could fulfill its grand promise. It could be “more than wires and lights in a box,” in the words of newsman Edward R. Murrow, and not just the “vast wasteland” that Federal Communications Commission chairman Newton Minow had branded it just two years before.