In their first feature film, Unknown (which opened at the E Street Cinema on Friday), director Simon Brand and screenwriter Matthew Waynee demonstrate that they have absorbed the lessons of thrillers like Reservoir Dogs, True Romance, Memento, Pi, Sixth Sense, and The Usual Suspects. That is, a thriller’s thrill comes from delaying the audience’s understanding of the real circumstances and motivations of the characters as long as possible. If the screenplay can keep the characters…