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/views/dashboard/get-started.html

@@ -0,0 +1,19 @@
+{% from "components/banner.html" import banner_wrapper %}
+
+<h2 class="heading-medium">Get started</h2>
+<ol class="grid-row">
+  {% if current_user.has_permissions(['manage_templates']) %}
+    <li class="column-half">
+      {% call banner_wrapper(type="tip", subhead='1.' if not templates else None, with_tick=templates|length) %}
+        <a href='{{ url_for(".add_service_template", service_id=service_id, template_type="sms") }}'>Add a template</a>
+      {% endcall %}
+    </li>
+  {% endif %}
+  {% if current_user.has_permissions(['send_texts', 'send_emails', 'send_letters']) %}
+    <li class="column-half">
+      {% call banner_wrapper(type="tip", subhead='2.') %}
+        <a href='{{ url_for(".choose_template", service_id=service_id, template_type="sms") }}'>Send yourself a message</a>
+      {% endcall %}
+    </li>
+  {% endif %}
+</ol>