First draft of store API

The API needs to support:

- [ ] creating data stores (tables) with optional schema
- [ ] deleting data stores (tables)
- [ ] listing all stores and their schemas
- [ ] adding individual entries (rows) to stores
- [ ] delete individual entries (rows) from stores
- [ ] updating individual entries (rows) in stores
- [ ] retrieving individual entries (rows)
- [ ] bulk uploads of entry updates
- [ ] free text searching for entries in a store
- [ ] streaming all entries from a store that match a given query

Stores are associated with an account, which is identified by an account id.