"The Secret Garden" is headed to Broadway next season;  starry "To Kill A Mockingbird" cast announced; "The Sting", "Unmasked",  "Hundred Days", and "Chess" receive regional productions; Wayne Brady returns to "Kinky Boots"; Katharine McPhee will make Broadway debut in "Waitress"; Playwrights Horizons' 2018-2019 season announced; MCC Theater cuts ties with Neil LaBute; lights dim for Jan Maxwell