[WIP] Refuse to build if user is importing something that isn't declared in package.json

Created by: matoilic

This is a try to implement #1725. Currently it only enables the import/no-extraneous-dependencies ESLint rule. The challenge is now to find a way to force eslint-loader to revalidate invalid files when the package.json changes, e.g. when the user fixes a transitive dependency issue by adding the package to his or her own package.json.