Access url for interventions

* adds access_token as new attribute
* adds generating of access_token
* adds new form
* adds two new routes for sharing an intervention
* adds translation
* adds render_submit to BaseModalForm which triggers rendering the modal footer

templates/modal/modal_form.html

@@ -20,7 +20,9 @@
         </article>
         {% include 'table/generic_table_form_body.html' %}
     </div>
+    {% if form.render_submit %}
     <div class="modal-footer">
         <button type="submit" class="btn btn-default">{% trans 'Continue' %}</button>
     </div>
+    {% endif %}
 </form>