Revised the ResourceJSON, round 1.

Round 2 coming.
Revised the ResourceJSON, round 2.

Work on the relations will be needed, but getting the resources/collections working again will be more important.
Revised the test JSON to match the recent changes.
Updated the loader to parse the new way ResourceJSON files are stored.
Updated resources/collections to handle the updated JSON.
Changed how identifiers are handled (for better behavior on methods like ``.get(…)``).
Fixes for Py2.
Merge branch 're-rewrite-resources' into develop