Ability to return 401 and 403 response codes #301

added app and model settings `aclErrorStatus`
default to 403 on ACL Error
added tests
Signed-off-by: Karl Mikkelsen <karl@karlmikko.com>
I see. `strong-remoting` is not aware of models, thus it probably should not share the same error messages with loopback & loopback-datasource-juggler.

AFAIK loopback `Model` class is inheriting from juggler's `ModelBaseClass` ([source](https://github.com/strongloop/loopback-datasource-juggler/blob/master/lib/model.js)), perhaps the error methods can be defined there?