Add Edition field to classify branches versus releases

[jonathansick]

Having a concrete field to classify an edition as tracking a work branch versus a release is nice because it sets a single source of truth for things like LTD Dasher, and edition switching widgets in actual sites.

I think this should be a string field so that there can be an extensible set of edition “kinds”: releases, pre-releases, dailies/weeklies, and regular branches. Maybe even “deployment” if /v/ paths double as differentiating deployments.

The kind can either be declared by the client, or there can be a heuristic assigned to the product.