Rhett is the official costumed mascot of the Boston University (BU) and the Boston University Academy (BUA) Terriers, the often snarling, bi-pedal black and white Boston Terrier was later named after the male lead in Margaret Mitchell's "Gone with the Wind", because "No one loves Scarlett more than Rhett" referencing Rhett Butler's affection for which fictional character and the main protagonist in Margaret Mitchell's 1936 novel "Gone with the Wind" and in the later film of the same name?