Move JSON functionality into native

[battila7]

Brief

One of CryptID's most interesting capabilities is the support of JSON public keys. However, this functionality is currently only present in CryptID.js.

As it'd be appealing to make CryptID available outside of the browser, JSON handling should be moved to native.

Task

• Choose a lightweight, fast and easy-to-integrate C JSON library.
• Integrate the chosen library, so that clients can pass JSON strings as identities.

Note

Consider using jsmn