Added update action to System

NzbDrone.Web/Views/System/Index.cshtml

@@ -18,6 +18,7 @@
     <ul class="sub-menu">
         <li>@Ajax.ActionLink("Restart", "Restart", "System", null, null, new { Title = "Restart NzbDrone" })</li>
         <li>@Ajax.ActionLink("Shutdown", "Shutdown", "System", null, null, new { Title = "Shutdown NzbDrone" })</li>
+        <li>@Html.ActionLink("Update", "Index", "Update")</li>
         <li>@Html.ActionLink("Logs", "Logs", "System")</li>
     </ul>
 }