Add a JSON-Path Feature

[couchdeveloper]

When parsing a JSON document, oftentimes one is not interested in the complete JSON representation returned as a hierarchy of objects.

A json-path filter could be used to specify a "filter" when parsing - which returns JSON objects whose json-path matches that specified in the json-path filter.

The idea could be even more extended to also taking values of the JOSN object into account - using a predicate comprised of a json-path into the resulting object in order to identify the path to that value and perform a match on that value.

[couchdeveloper]

An experimental json-path feature is already in development.