When adding json fragment into generated json, validate it and isolate it
Allow to free SJsonGen
Make sure true/false/null that are part of a name (like nullable:bla) are scanned correctly in s_json_buildv
Isolate input json in s_json_compact
Expand test coverage of compact/pretty and build with unquoted strings
Optimize pretty/fix compact on fragment
Added s_json_gen_member