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.
Maybe call this "meta" for consistency with items?