[Other] Extract the ORM to a new library

The created ORM is inspired by `redux-orm` but has a number of interesting differences:
- out of the box support for create-react-app (which `redux-orm` lacked at the time).
- bi-directional relationships between models
- the object store is far less opaque, for example it is accessed directly in selectors, not via the ORM as with `redux-orm`.
- quirky in that only a single model result can be in context on each given model at once. Models are more or less singleton instances of their respective declared model classes. This is probably the main caveat, and may not suit everyone.
- slightly different configuration of e.g. default values.

It should be extracted from aperitif-editor, so that it can be maintained separately.