Philip Shenon, author of “A Cruel and Shocking Act: Secret History of the Kennedy Assassination,” is among the experts who are eagerly awaiting the scheduled release Thursday of thousands of documents related to the assassination of President John F. Kennedy. Shenon, who spent more than 20 years writing for The New York Times, told the Herald’s Owen Boss about what he hopes the documents will reveal and the details that will shed light on one of America’s most infamous events.