Send HTML confirmation emails.

Also tidy up the PDF and some of the source.

RIGS/templates/RIGS/eventauthorisation_client_success.html

@@ -0,0 +1,23 @@
+{% extends 'base_client_email.html' %}
+
+{% block content %}
+    <div class="col-sm-12">
+        <p>Hi {{ to_name|default:"there" }},</p>
+
+        <p>
+            Your event N{{ object.event.pk|stringformat:"05d" }} has been successfully authorised
+            for {{ object.amount }}
+            by {{ object.name }} as of {{ object.last_edited_at }}.
+        </p>
+
+        <p>
+            {% if object.event.organisation and object.event.organisation.union_account %}{# internal #}
+                Your event is now fully booked and payment will be processed by the finance department automatically.
+                {% else %}{# external #}
+                Your event is now fully booked and our finance department will be contact to arrange payment.
+            {% endif %}
+        </p>
+
+        <p>TEC PA & Lighting</p>
+    </div>
+{% endblock %}