Put uploaded files on the dashboard

This commit depends on and uses the data returned by:
- [x] https://github.com/alphagov/notifications-api/pull/345
- [x] https://github.com/alphagov/notifications-api/pull/347
- [x] https://github.com/alphagov/notifications-admin/pull/612

It puts the last 5 jobs on the dashboard. This should be changed to all the jobs
from the last 7 days when that parameter is available.

It also:
- links to the jobs page
- makes the numbers on the jobs page consistent with the dashboard
- makes the numbers on an individual job consistent with the appearance of the
  dashboard

app/templates/components/big-number.html

@@ -14,7 +14,7 @@
     {% if label_link %}
       <a class="big-number-label" href="{{ label_link }}">{{ label }}</a>
       <a class="big-number-overlay-link" href="{{ label_link }}" aria-hidden="true"></a>
-    {% else %}
+    {% elif label %}
       <span class="big-number-label">{{ label }}</span>
     {% endif %}
   </div>