How's this for a niche network - a TV audience of 2.6-million, all dressed in fatigues. The Pentagon Channel has been a favorite with the troops for years. But these days you don't need a crew cut to watch it. All you need to do is tune in to Pinellas County's Channel 18 at 5:30 p.m. six days a week. The Pentagon Channel's 24-hour news programming was originally aimed at American troops. But the U.S. Department of Defense recently has enlisted public and government access cable channels to help spread its message, including Channel 18. The county-run cable channel began...