Add a meta-only response class and add `withServer` method to all response classes

[lindyhopchris]

At the moment we are missing a response class for a meta-only response.

We also need to add a withServer method on our response, so that you can manually set the server that should be used to encode the response. This is needed if you are using the response classes outside of the JSON:API middleware. In such scenarios, you get an error because the responses try to get the jsonapi top-level document object from the server bound in the container, which is missing if the middleware hasn't been run.