Better i18n for due/available time format

There are various different such format strings here. But they all result in the same format. So combine them into only two.

openassessment/templates/openassessmentblock/response/oa_response.html

@@ -18,7 +18,7 @@
                 {% elif submission_due %}
                 <span class="step__deadline">
                     {# Translators: This string displays a date to the user, then tells them the time until that date.  Example: "due August 13th, 2014 (in 5 days and 45 minutes)" #}
-                    {% blocktrans with due_date=submission_due|utc|date:"N j, Y H:i e" time_until=submission_due|timeuntil %}due <span class="date"> {{ due_date }} (in {{ time_until }})</span>{% endblocktrans %}
+                    {% blocktrans with due_date=submission_due|utc|date:"N j, Y H:i e" time_until=submission_due|timeuntil %}due <span class="date">{{ due_date }} (in {{ time_until }})</span>{% endblocktrans %}
                 </span>
                 {% endif %}
             </span>

openassessment/templates/openassessmentblock/self/oa_self_assessment.html

@@ -18,7 +18,7 @@
                 {% elif self_due %}
                 <span class="step__deadline">
                     {# Translators: This string displays a date to the user, then tells them the time until that date.  Example: "due August 13th, 2014 (in 5 days and 45 minutes)" #}
-                    {% blocktrans with due_date=self_due|utc|date:"N j, Y H:i e" time_until=self_due|timeuntil %}due <span class="date">{{ due_date }}</span> (in {{ time_until }}){% endblocktrans %}
+                    {% blocktrans with due_date=self_due|utc|date:"N j, Y H:i e" time_until=self_due|timeuntil %}due <span class="date">{{ due_date }} (in {{ time_until }})</span>{% endblocktrans %}
                 </span>
                 {% endif %}
             </span>

openassessment/templates/openassessmentblock/student_training/student_training.html

@@ -13,12 +13,12 @@
                 {% if training_start %}
                     <span class="step__deadline">
                         {# Translators: This string displays a date to the user, then tells them the time until that date.  Example: "available August 13th, 2014 (in 5 days and 45 minutes)" #}
-                        {% blocktrans with start_date=training_start|utc|date:"N j, Y H:i e" time_until=training_start|timeuntil %}available <span class="date"> {{ start_date }} (in {{ time_until }}) </span>{% endblocktrans %}
+                        {% blocktrans with start_date=training_start|utc|date:"N j, Y H:i e" time_until=training_start|timeuntil %}available <span class="date">{{ start_date }} (in {{ time_until }})</span>{% endblocktrans %}
                     </span>
                 {% elif training_due %}
                     <span class="step__deadline">
                         {# Translators: This string displays a date to the user, then tells them the time until that date.  Example: "due August 13th, 2014 (in 5 days and 45 minutes)" #}
-                        {% blocktrans with due_date=training_due|utc|date:"N j, Y H:i e" time_until=training_due|timeuntil %}due <span class="date">{{ due_date }}</span> (in {{ time_until }}){% endblocktrans %}
+                        {% blocktrans with due_date=training_due|utc|date:"N j, Y H:i e" time_until=training_due|timeuntil %}due <span class="date">{{ due_date }} (in {{ time_until }})</span>{% endblocktrans %}
                     </span>
                 </span>
                 {% endif %}