Make data consistent from dashboard -> job

- adds a table of recent activity to the job page, which is shared by the
  dashboard page
- uses the same filename and message template as the first job shown on the
  dashboard
- sets the time of file uploads/message delivery/message sending to always
  match ‘just now’

tests/app/main/views/test_dashboard.py

@@ -0,0 +1,6 @@
+def test_should_show_recent_jobs_on_dashboard(notifications_admin):
+    response = notifications_admin.test_client().get('/dashboard')
+
+    assert response.status_code == 200
+    assert 'Test message 1' in response.get_data(as_text=True)
+    assert 'Asdfgg' in response.get_data(as_text=True)