Unify service return values

The get|post|put|* REST API methods aren't consistent about return values. For example put can return a boolean, the stringified response body or the response object. It would be good to make those consistent. Also it would be good to always return the response so that the caller can elect to resubmit the request with different parameters if needed. If the method also returns an entity, then have the method return an array containing [response, entity].