Trace Adkins and Kris Kristofferson will star alongside Luke Hemsworth and Bruce Dern in the upcoming Western, Hickok, which opens in theaters and on demand on July 7. The new flick features Wild Bill Hickok (Hemsworth) in 1870s Abilene, Kan., where mayor George Knox (Kristofferson) recruits the gunslinger to be the town marshal. Hickok soon…