Various tweaks

- remove black border from banner
- make banners have internal columns
- make nav 2/3rd width, 19px text and more spaced out
- only show the ‘restricted mode’ banner where it’s needed
- rename ‘restricted mode’ to ‘trial mode’

app/templates/views/api-keys.html

@@ -22,6 +22,12 @@
     developer documentation</a>.
   </p>
 
+  {{ banner(
+    'You can only send notifications to yourself',
+    subhead='Trial mode',
+    type='info'
+  ) }}
+
   <h2 class="api-key-name">
     Service ID
   </h2>