Proper endpoints for persistent notifications

closes #2637
- Add new get API route for all notifications
- Wrap API responses to comply with JSON-API
- Add new tests / adjust fixtures
- Adjust all occurences of passive notifications
Merge pull request #2665 from halfdan/2637-persistent-notifications

Proper endpoints for persistent notifications
Consistency in model method naming

- The API has the BREAD naming for methods
- The model now has findAll, findOne, findPage (where needed), edit, add and destroy, meaning it is similar but with a bit more flexibility
- browse, read, update, create, and delete, which were effectively just aliases, have all been removed.
- added jsDoc for the model methods