gui: Vertically center identicons in panel titles

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3256

gui/default/index.html

@@ -135,7 +135,7 @@
         <div class="panel panel-warning">
           <div class="panel-heading">
             <h3 class="panel-title">
-              <identicon data-value="device"></identicon>
+              <identicon class="panel-icon" data-value="device"></identicon>
               <span translate>New Device</span>
               <span class="pull-right">{{ event.time | date:"yyyy-MM-dd HH:mm:ss" }}</span>
             </h3>