Added templates for http exceptions.

dav_events/templates/403.html

@@ -0,0 +1,8 @@
+{% extends "error_base.html" %}
+
+{% block error-code %}403{% endblock %}
+{% block error-title %}Forbidden{% endblock %}
+{% block error-heading %}Keine Berechtigung{% endblock %}
+{% block error-body %}
+<p>Irgendwas darfst du hier nicht.</p>
+{% endblock %}