shield to allow full access to filters; fixes to engines ; docs; tests
shield to allow full access to filters; fixes to engines ; docs; tests

mugitty/bbop-js,mugitty/bbop-js,berkeleybop/bbop-js,berkeleybop/bbop-js,berkeleybop/bbop-js,mugitty/bbop-js,mugitty/bbop-js,berkeleybop/bbop-js,mugitty/bbop-js,berkeleybop/bbop-js