added empty list cta to notification channels, fixes 10393 (#10400)

public/app/features/alerting/partials/notifications_list.html

 <page-header model="ctrl.navModel"></page-header>
 
 <div class="page-container page-body">
+
+  <div ng-if="ctrl.notifications.length">
     <div class="page-action-bar">
       <div class="page-action-bar__spacer">
       </div>
@@ -42,4 +44,17 @@
         </tr>
       </tbody>
     </table>
+  </div>
+  <div ng-if="ctrl.notifications.length === 0">
+    <empty-list-cta model="{
+      title: 'There are no notification channels defined yet',
+      buttonIcon: 'gicon gicon-alert-notification-channel',
+      buttonLink: 'alerting/notification/new',
+      buttonTitle: 'Add channel',
+      proTip: 'You can include images in your alert notifications.',
+      proTipLink: 'http://docs.grafana.org/alerting/notifications/',
+      proTipLinkTitle: 'Learn more',
+      proTipTarget: '_blank'
+    }" />
+  </div>
 </div>