Use production Organisations API except in test

In dev, we don't want to incur the cost of depending on Whitehall just for the organisations API.
In test, the organisations API stubs assume that the basepath is `Plek.current.find("whitehall-admin")`.
In preview, the client would have to handle simple auth so pointing to production is simpler.
Calculate manual update type from section update types

A manual update is major if there are any major section updates.