Add an option to honor emailVerified

/to @ritch or @bajtos 
The PR should supersedes https://github.com/strongloop/loopback/pull/215
Same comment as above. Since this is used in multiple places, perhaps you can move it to a `beforeEach` or `afterEach` hook?

```js
beforeEach(function resetEmailVerificationRequired() {
  User.settings.emailVerificationRequired = false;
});
```