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>
A problem arises as strong-remoting passes through the errors from loopback and the loopback-data-source-juggler through to the end user. I think in these cases the errors should be the same.

On a side note, the other day I was working on some client side code (Javascript not angular) and had the need to replicate a 404 error that loopback would produce. I had to reproduce this error in my code - I would have loved to just import an errors module.