Implement full unicode in \uXXXX format

[James Powell]

See https://forums.ni.com/t5/LabVIEW/Mixed-JSON-and-UNICODE-trouble/m-p/4247621

See note “<ToDo>Handle full Unicode” in Unescape JSON String.vi

[James Powell]

Implemented, BUT, LabVIEW Windows isn’t utf-8. We may need a way to get full unescaped UTF-8 strings (perhaps a <UTF8> tag).

[James Powell]

See #210 which impliments that <UTF8> tag