Add some visual indicators that authorisations have been submitted.

This will show teccies and clients that RIGS is processing emails which can take a short while.
Should prevent duplicate sending.

RIGS/templates/RIGS/eventauthorisation_form.html

@@ -7,7 +7,14 @@
     <script>
         $(function () {
             $('[data-toggle="tooltip"]').tooltip();
-        })
+        });
+
+        $('form').on('submit', function() {
+           $('#loading-modal').modal({
+               backdrop: 'static',
+               show: true
+           });
+        });
     </script>
 {% endblock %}