Work in progress for the Drupal 8 version of https://www.drupal.org/project/campaignmonitor Drupal.org issue https://www.drupal.org/node/2300625
Notes:
- Does not contain the submodules campaignmonitor_registration and campaignmonitor_user
- The bulk of the work here as converting campaignmonitor wrapper class to use drupal 8 functions and also porting over the admin settings form.