Need serialization function

[JanWielemaker]

We need to define Pengine.stringify(), which takes a JavaScript object and stringifies it properly in a suitable form for Prolog. In particular,

• numbers are simple
• strings must be translated to an atom of string (at user request)
• arrays must be translated into a Prolog list
• objects must be translated into a dict.

[JanWielemaker]

Is provided as Pengine.stringify(data, options)