Remove SCHEMA to simplify database interaction

Instead of using a separate schema, we now simply use different databases. This removes the need to specify the schema / search_path in various places, which is quite a brittle approach IMO. The relationship is like this:

Postgres DBOD instance > Database > Schema > Table

Additionally, we create user accounts that only have access to their particular database (least-privilege principle).

Let me know if all of this is clear enough from the documentation I have updated.