Put some statistics on the dashboard

This commit adds two new sections to the dashboard

1. A banner telling you about trial mode, including a count of how many messages
   you have left today, which is a restriction of trial mode

2. Panels with counts of how many emails and text messages have been sent in a
   day, plus the failure rates for each

It does **not**:
- link through to any further information about what trial mode is (coming
  later)
- link through to pages for the failure rates (coming later)
- change the ‘recent jobs’ section to ‘recent notifications’

app/templates/components/big-number.html

@@ -4,3 +4,14 @@
     <span class="big-number-label">{{ label }}</span>
   </div>
 {% endmacro %}
+
+
+{% macro big_number_with_status(number, label, status_number, status_label, percentage_bad=0) %}
+  <div class="big-number-with-status">
+    {{ big_number(number, label) }}
+    <div class="big-number-status">
+      <div class="big-number-status-error-percentage" style="opacity: {{ percentage_bad / 100 }}"></div>
+      {{ big_number(status_number, status_label) }}
+    </div>
+  </div>
+{% endmacro %}