LUA: Replace DKJSON by a C based version to improve performance

Hello,

The more you advance in coding with lua, the more you will be confronted with the use of the JSON library.
The library currently used is an implementation of JSON in Lua. It does not perform well and leads to a lot of CPU overhead.

Lua allows to include C libraries which are much more powerful than Lua code.

It would be good to replace the current library "DKJson" by the library "Lua CJSON" or "Lua RapidJSON".
In performance we will gain enormously on processing speed and memory management will also be improved.

Some links to benchmarks:
https://www.kyne.com.au/~mark/software/lua-json-performance.html
https://github.com/Tencent/rapidjson/issues/275#issuecomment-183876920

Under consideration Suggested by: Leniver Upvoted: 28 Apr, '21