Some might call “The Revisionists: A Haunted Victorian Walk” a charming amble about the grounds of Rockwood Park. Producer Gregory Shelton calls it “a live-action mobile theater macabre play.” The latest addition to New Castle County’s lineup of Halloween thrills, “The Revisionists” is part whodunnit and part spooky frights meant for those aged 13 and older. “It’s not blood-and-guts slasher …