API SSO, Beautification of Tables, and more. (#562)

# One Thousandth Commit 🎉 🎈 🎆 🍾

* Allow requiring API ownership validation by SSO.
Closes #163

* Add Discourse group name length restrictions.

* Redirect after api addition/deletion of main character

* Correct admin searching for removed discourse_username field in AuthServicesInfo

* Correct admin function to sync user Discourse groups

* Beautify tables by removing borders and hiding when empty.

*Add buttons on dead-end pages to return to originating view.

stock/templates/registered/notification_view.html

@@ -8,7 +8,14 @@
 {% block content %}
 
     <div class="col-lg-12">
-        <h1 class="page-header text-center">{% trans "View Notification" %}</h1>
+        <h1 class="page-header text-center">
+            {% trans "View Notification" %}
+            <div class="text-right">
+                <a href="{% url 'auth_notification_list' %}" class="btn btn-primary btn-lg">
+                    <span class="glyphicon glyphicon-arrow-left"></span>
+                </a>
+            </div>
+        </h1>
         <div class="col-lg-12 container" id="example">
             <div class="row">
                 <div class="col-lg-12">