refs https://github.com/TryGhost/Team/issues/584
refs https://github.com/TryGhost/Team/issues/1498
- updated newsletter save routine in `edit-newsletter` modal to open an email confirmation modal if the API indicates one was sent
- modal indicates that the previously set or default email will continue to be used until verified
- response from API when saving looks like `{newsletters: [{...}], meta: {sent_email_verification: ['sender_name]}}`
- added custom newsletter serializer and updated model so that the `meta` property returned in the response when saving posts is exposed
- Ember Data only exposes meta on array-response find/query methods
- https://github.com/emberjs/data/issues/2905
- added `/settings/members-email-labs/?verifyEmail=xyz` query param handling
- opens email verification modal if param is set and instantly clears the query param to avoid problems with sticky params
- when the modal opens it makes a `PUT /newsletters/verify-email/` request with the token in the body params, on the API side this works the same as a newsletter update request returning the fully updated newsletter record which is then pushed into the store
- removed unused from/reply address code from `<Settings::MembersEmailLabs>` component and controller
- setting the values now handled per-newsletter in the edit-newsletter modal
- verifying email change is handled in the members-email-labs controller
- fixed mirage not outputting pluralized root for "singular" endpoints such as POST/PUT requests to better match our API behaviour
