WIP: Changes needed for ORCID OAuth component

• Export an index of all the models, for use as app.locals.models (#16)
• Add name and orcid to the User validations. Ideally the component would be able to add the "orcid" validation, rather than it being specified here. See https://gitlab.coko.foundation/pubsweet/pubsweet-backend/issues/19 for discussion of username vs name.