Consider fundamental alteration of action method structure

[pond]

Perhaps e.g. go with return ... and the returned item is either auto-rendered, or is the rendering of the resource, but either way no explicit context.response.set_resource. It's implicitly singular for any action other than list, else plural. Declarative access to estimation counts, but since estimation counts seem to be basically useless maybe drop that entirely.

Just a placeholder for some deeper thinking about whether or not we break the API's backwards compatibility in V2 deeply, because it's really worth it in terms of reducing boilerplate with 3 years of hindsight now.