Mail sending

* adds mail sending logic for new notification setting
* adds new templates for user and team based sending
* enhances all email template layout
* adds translations

templates/email/sharing/shared_access_removed_team.html

@@ -7,6 +7,7 @@
     <article>
         {% trans 'Hello team' %} {{team.name}},
         <br>
+        <br>
         {% trans 'your teams shared access, including editing, has been revoked for the dataset ' %}
         <br>
         <strong>{{obj_identifier}}</strong>