feat(notification): add helptext for using multiple email addresses

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

@@ -24,7 +24,12 @@
         </div>
       </div>
       <div class="gf-form">
-        <gf-form-switch class="gf-form" label="Send on all alerts" label-class="width-12" checked="ctrl.model.isDefault" tooltip="Use this notification for all alerts">
+        <gf-form-switch
+           class="gf-form"
+           label="Send on all alerts"
+           label-class="width-12"
+           checked="ctrl.model.isDefault"
+           tooltip="Use this notification for all alerts">
         </gf-form-switch>
       </div>
     </div>
@@ -65,6 +70,9 @@
       <div class="gf-form">
         <textarea rows="7" class="gf-form-input width-25" required ng-model="ctrl.model.settings.addresses"></textarea>
       </div>
+      <div class="gf-form">
+        <span>You can center multiple email address using a ";" seperator</span>
+      </div>
     </div>
 
     <div class="gf-form-group">