> This makes models useful only if an app is available... I'm not entirely against this, but would like to justify the added constraint.

There is another angle to this: how to group a set of loopback Models into a package that can be shared between projects.

In the current solution, `models/` is not a standalone package, it does not export anything. It expects that `app.boot()` will pick up `model.json` and `models/*` and do whatever is necessary to setup the models in the app.

To create a package of Modules, one has to use different APIs, i.e. manually call `Model.extend` or `DataMode.extend` as was done in the previous revision.

We could come up with a project layout that will keep all models-related files in a single place (a single npm package) and then implement a mechanism for declaratively adding all/selected models from such package to a loopback app. However, I don't think we have enough time for that now, IMO this is closer to "nice to have" than to "must have".