Discovery: Plan for drupal 8 feedback module

[janette]

• As an anonymous user I can add feedback to datasets
• As an anonymous user I can see a list of published feedback
• As an anonymous user I can see the feedback related to a dataset in the dataset page
• As an administrator user I can publish, archive and delete feedback
• As an authenticated user I can comment on feedback.
• As an administrator user I can publish, archive and delete feedback comments.

(Optional):

• As a site manager I can add an email address to notify about incoming feedback, and receive notifications to that address, so that I can more easily respond.