Show full email template on single template page

There’s no point in collapsing […] the email on the single template
page because it’s the only thing on the page.

Users will probably be going back and forth quite a bit to edit their
template and see the changes; they shouldn’t have to expanded it evey
time to check they’ve got the heading syntax right, for example.

app/templates/views/templates/_template.html

@@ -6,7 +6,8 @@
     {{ email_message(
       template.formatted_subject_as_markup,
       template.formatted_as_markup,
-      id=template.id
+      id=template.id,
+      expanded=expanded
     ) }}
   {% elif 'sms' == template.template_type %}
     {{ sms_message(

app/templates/views/templates/template.html

@@ -14,7 +14,7 @@
   <h1 class="heading-large">{{ template.name }}</h1>
 
   <div class="grid-row">
-    {% with show_title=False %}
+    {% with show_title=False, expanded=True %}
       {% include 'views/templates/_template.html' %}
     {% endwith %}
   </div>