adding 'block header' abstration to peer/self assessment step templates

apps/openassessment/templates/openassessmentblock/oa_peer_assessment.html

@@ -17,6 +17,7 @@
         {{ peer_submission.uuid }}
     </span>
 
+    {%  block header %}
     <header class="step__header ui-toggle-visibility__control">
         <h2 class="step__title">
             <span class="step__counter"></span>

apps/openassessment/templates/openassessmentblock/oa_self_assessment.html

@@ -14,6 +14,8 @@
 {% block list_item %}
 <li id="openassessment__self-assessment" class="openassessment__steps__step step--self-assessment">
 {% endblock %}
+
+    {%  block header %}
     <header class="step__header">
         <h2 class="step__title">
             <span class="step__counter"></span>
@@ -28,6 +30,8 @@
           <span class="step_status_value">Incomplete</span>
         </span>
     </header>
+    {% endblock %}
+
     {% block body %}
     <div class="step--content">
         <article class="self-assessment" id="self-assessment">