In a radio schedule packed with dangerous dames and gat-toting gumshoes, “Dragnet” was a strikingly different and provocative program that took an inside look at the everyday work of police officers. Deliberately understated and low-key, the series was created by and stars Jack Webb as Sergeant Joe Friday — an average cop who spends his days — and often his nights — working with his colleagues to investigate serious crimes. Setting aside the slam-bang dramatics that were a staple of most detective shows, “Dragnet”