resource_show does not suport GET

Going to `http://demo.ckan.org/api/action/package_show?id=foo` returns json.
Going to `http://demo.ckan.org/api/action/resource_show?id=foo` returns `"Bad request - JSON Error: No request body data"`.

POST requests work as expected.

The problem is that the datastore overwrites the `resource_show` method to inject some information. The method is not marked side effect free, though.