[C++] JSON serialization

[ksergey]

Hello SBE devs!

SBE codec is not escapes characters reserved by JSON during serialization.
It produces invalid JSON in cases when symbols like " present in text fields.

Thanks

[mjpt777]

This is not something we make use of. Feel free to send a PR to address it.

[rigtorp]

There is no builtin JSON serialization in the C++ codecs is there?

[ksergey]

@rigtorp there is JSON-like serialization. Serialization code don't escape JSON control chars in strings.

[ksergey]

I think better solution to have something like exists in rapidjson library:
https://rapidjson.org/md_doc_sax.html#Reader

[mjpt777]

I've pushed a change which will Json escape var data strings in UTF-8 or ASCII will is a subset and this is use for the pretty printing. Raw binary will be summarised as "x bytes of raw data".