Evaluate a Drupal8 upgrade

Scope: evaluate (roughly) how much work would be involved in upgrading civicrm.org to Drupal8. This is only to help make a more informed decision of: do we stay on d7 for a long time, upgrade to d8, or move to WordPress.

Why: we want to enable multilingual, which is a fairly big change in the configurations. We will need to upgrade sooner or later (within 1-3 years). If we enable multilingual now, and invest non-trivial energy in translation etc, we will be further locked-in the current solution.