Show template usage for all time on it’s own page

> We show the last weeks template usage on the dashboard, which is
> great, but if you're looking for longer term trends, you're out of
> luck...

> So, let's let you see more on a more detailed page (linked from the
> dashboard). Initially this should just show you all templates that you
> have used ever and the count for each. Order same as dashboard, most
> popular first.

https://www.pivotaltracker.com/story/show/117614585

app/templates/views/dashboard/template-statistics.html

@@ -3,7 +3,7 @@
   template_statistics,
   caption="By template",
   caption_visible=False,
-  empty_message='You haven’t set up any templates yet',
+  empty_message='You haven’t used any templates {}'.format(period),
   field_headings=['Template', hidden_field_heading('Type'), right_aligned_field_heading('Messages processed')]
 ) %}
   {% call field() %}