[#278] Native JSON support

[Jubilee101]

A native json libray, supports:

1. Multiple data types: int64, string, float, corresponding arrays, as well as nested json objects.
2. Basic operations to init, search, insert, update json fields
3. Shallow parsing, parse the json file to a json item. All nested json objects will be ignored for now (we don't need them anyway)
4. Navigating. Provided with an array of keys as path, navigate to where the json array or item starts. This uses bounded memory, no need to load the whole json file into memory at a time.
5. Iterative item array parsing. Parse items within one at a time. This uses bounded memory, no need to load the whole json file into memory at a time.
6. Format printing

[jesperpedersen]

Merged.

Thanks for your contribution !