Fix #707 -- Setup automated spell-checking for translations (#896)

This will:
  * set up potypo
  * add wordlists, edgecases and phrases
  * fix english typos across the codebase
  * fix german typos and translation

src/pretix/control/templates/pretixcontrol/auth/login_2fa.html

@@ -8,7 +8,7 @@
         {% csrf_token %}
         <h3>{% trans "Welcome back!" %}</h3>
         <p>
-            {% trans "You configured your account to require authentification with a second medium, e.g. your phone. Please enter your verification code here:" %}
+            {% trans "You configured your account to require authentication with a second medium, e.g. your phone. Please enter your verification code here:" %}
         </p>
         <div class="form-group">
             <input class="form-control" name="token" placeholder="{% trans "Token" %}"

src/pretix/control/templates/pretixcontrol/multi_languages_widget.html

@@ -11,7 +11,7 @@
         </span>
     {% elif not widget.official %}
         <span class="label label-warning" data-toggle="tooltip" title="{% trans "This translation is not maintained by the pretix team. We cannot vouch for its correctness and new or recently changed features might not be translated and will show in English instead. You can help translating at translate.pretix.eu." %}">
-            {% trans "Inofficial translation" %}
+            {% trans "Unofficial translation" %}
         </span>
     {% endif %}
     </label>

src/pretix/control/templates/pretixcontrol/organizers/team_delete.html

@@ -4,7 +4,7 @@
 {% block inner %}
     <h2>{% trans "Delete team:" %} {{ team.name }}</h2>
     {% if not possible %}
-        <p>{% blocktrans %}You cannot delete the team because there would be noone left who could change team permissions afterwards.{% endblocktrans %}</p>
+        <p>{% blocktrans %}You cannot delete the team because there would be no one left who could change team permissions afterwards.{% endblocktrans %}</p>
         <div class="form-group submit-group">
             <a href="{% url "control:organizer.teams" organizer=request.organizer.slug %}" class="btn btn-default btn-cancel">
                 {% trans "Cancel" %}