[WIP] Jobs

@cjh1 in case you want to keep an eye on this, this PR adds

- A general purpose data model and REST API for batch job management
- Scoped token support, including supporting authorization for clients that do not have a corresponding user document.
- Making `ModelImporter.model` a static method so that it can be called more easily outside of objects that have ModelImported mixed in.
There are a lot of different Celery setting that the user might want to pass when initializing the Celery app. Is the a generic way we can provide access to all these without having to enumerate them here?