dbconn: Refactor connection methods
Created by: efritz
This PR makes the set of exported methods used to connect to the database very obvious:
-
ConnectRaw
is used for dev tools (e.g., sg, schemadoc) and unit tests -
New{Name}DB
is used to create a connection to a database with a particular expected schema. For now, these calls will attempts to migrate the database to the expected version (just as the frontend does today).