Create pcnspec_jsonschema.json

Formal specification of the PCN Spec according to JSON Schema, a draft standard of the IETF. This file can be imported by JSON Schema validators and related tools to validate and process PCN Spec documents. See http://json-schema.org/.
edit description
JSON Schema Validation

Add explanation of validation using JSON Schema
Merge pull request #16 from yhack/patch-1

PCN Spec specified according to JSON Schema specification