Refs #39 -- New concept of "teams" (#478)

* New models

* CRUD UI

* UI for adding/removing team members

* Log display for teams

* Fix invitations, move frontend

* Drop old models (incomplete)

* Drop more old stuff

* Drop even more old stuff

* Fix tests

* Fix permission test

* flake8 fix

* Add tests fore the new code

* Rebase migrations

src/pretix/control/templates/pretixcontrol/items/quota.html

@@ -6,7 +6,7 @@
 {% block inside %}
     <h1>
         {% blocktrans with name=quota.name %}Quota: {{ name }}{% endblocktrans %}
-        {% if request.eventperm.can_change_items %}
+        {% if 'can_change_items' in request.eventpermset %}
             <a href="{% url "control:event.items.quotas.edit" event=request.event.slug organizer=request.event.organizer.slug quota=quota.pk %}"
                     class="btn btn-default">
                 <span class="fa fa-edit"></span>