I added the "metaformatters" flag prefixes %J (JSON.stringify()), %c and %C (color and color + bold (node)) as I proposed here #582 (comment), however I'm not 100% on it (they could just as well stay special-case-flags), so it should be easy to revert

Also, I'm not sure what to do about node's formatters %o / %O coloring (based on DEBUG_COLORS and isatty()), and passing other inspectOpts