New features

• Added favicon
• added adminimal-custom.css:
  In ressources/css there is a adminimal-custom.css that match the
  color scheme of this theme. To use it copy it in files folder and tick
  "Use adminimal-custom.css" in /admin/appearance/settings/adminimal_theme.
  This is a native feature of the Adminimal theme.
• corrected ugly spacing on the front-page view.

• Created a configuration form that allows:
  • Choosing whether to load library via CDN or not (default is local).
  • Adding a list of CSS selectors.
  • Specify whether to include the widget on all pages, only admin ones, or only frontend ones.
• Created a facets submodule which provides a Facets widget for loading Choices.js.

#3135320: Add views relationship from revisions back to content

First port for drupal 8.

I intentionally skipped the API part. Simple is better then complex.

Added support for sending mails for the user module.

Changes since 8.x-2.4: