Constant ptree::print_config::UTF_CHARS_BOLD

pub const UTF_CHARS_BOLD: StaticIndentChars = StaticIndentChars{down_and_right: "┣",
                  down: "┃",
                  turn_right: "┗",
                  right: "━",
                  empty: " ",}

UTF-8 indentation characters, using heavy box-drawing characters