Schema naming

Moved api schema and related tests around to make the namespaces consistent as per https://github.com/7digital/SevenDigital.Api.Wrapper/issues/45

Namespaces should be concise (so no "Endpoint" suffix) and should not duplicate the class name as this makes these types harder to use.

The agreed format is that the folder and matching namespace is the plural of the main entity inside it. e.g. the `Basket` class is in the `Baskets` folder.

The only place that this has issues is that there was a class called `Tags` which I renamed to `TagsResponse` in the `Tags` folder. Are there better options for this name?