lib: json: Parse nested objects and arrays

Parse arrays and nested objects.

Array parsing is limited to items of the same type, and requires an array
with fixed number of elements.  Elements can be of any type supported by
the parser, including arrays and objects.

The return value of json_obj_parse() won't be that helpful: the nth bit
will only be set if the object has been fully decoded.

Jira: ZEP-1607
Change-Id: I472e402ae3f36a1bd1505decc0313f74cbfa2e07
Signed-off-by: Leandro Pereira <leandro.pereira@intel.com>