(PUP-1151) Consolidate JSON schema validation

This adds a new matcher to the JSONMatchers to validate json against a
given json-schema. All of the json schema validation now goes through
this one matcher, which also handles skipping the checks on windows.
Merge pull request #2259 from zaphod42/feature/master/pup-1151-environment-enumeration

(PUP-1151) Consolidate JSON schema validation