removed fixture based backup

many different things can lead to this method of backing up failing both on backup and on restore.
to not give the user a false sense of security this feature was removed for the time being.
once i have time i will add a proper backup system.

cookbook/templates/system.html

@@ -22,6 +22,7 @@ <h3>{% trans 'Invite Links' %}</h3>
             <a href="{% url 'list_invite_link' %}" class="btn btn-success">{% trans 'Show Links' %}</a>
 
         </div>
+        <!--
         <div class="col-md-6">
             <h3>{% trans 'Backup & Restore' %}</h3>
             <a href="{% url 'api_backup' %}" class="btn btn-success">{% trans 'Download Backup' %}</a>
@@ -37,6 +38,7 @@ <h3>{% trans 'Backup & Restore' %}</h3>
             </div>
 
         </div>
+        -->
     </div>
 
     <br/>