Add messages to the current job’s history

This mocks out a data structure for a job’s messages, and renders this data:
- on the notification page, as a table, which links through to…
- …the page for an indidivual message

app/templates/views/job.html

@@ -13,7 +13,9 @@ GOV.UK Notify | Notifications activity
 			{{ uploaded_file_name }}
 		</h1>
 
+		<p>
     {{ banner(flash_message) }}
+		</p>
 
 		<ul class="grid-row job-totals">
 			<li class="column-one-third">