Id, Ref and File foreign normalization

We've started noticing this as we went along and became more familiar with proper database design:

Ref.from_id and to_id should point to Id
File should be removed when deleted: github.com/ourbigbook/ourbigbook/issues/216 Currently this can only happen locally. Edit: will also start happening on upstream with synonym moves.
toplevel_id
- File.toplevel_id should point to an Id object via primary key. Currently done via idid text.
- Id.toplevel_id should point to an Id object. No links at all apparently.
Article.topicId should point to Topic.id, not be TEXT

We could then consider removing several Ref.destroy and Id.destroy ON CASCADE with File and Id, rather than manually.

 Ancestors