Disable client-side validation on credit_note forms

* HTML5 browsers have some clevers to do client-side validation of
  forms
* Django activates this by default for certain field types
* However, in this case, there are three forms on this page. We rely
  on two of them being invalid in order to figure out what processing
  to do.
* So we need to disable the client-side validation.

pinaxcon/templates/registrasion/credit_note.html

@@ -18,7 +18,7 @@
 <p>This credit note was generated from funds excess from invoice {{ credit_note.invoice.id }}.</p>
 
 {% if credit_note.is_unclaimed %}
-  <form class="form-horizontal" method="post" action="">
+  <form class="form-horizontal" method="post" action="" novalidate>
     {% csrf_token %}
     <h3>Apply to invoice</h3>
     <p>You can apply this credit note to an unpaid invoice.</p>