Add aria label on cog (closes #1020)

gui/index.html

@@ -47,7 +47,7 @@
           </button>
         </li>
         <li class="dropdown">
-          <a href="#" class="dropdown-toggle" data-toggle="dropdown"><span class="glyphicon glyphicon-cog"></span></a>
+          <a href="#" class="dropdown-toggle" data-toggle="dropdown"><span class="glyphicon glyphicon-cog" aria-label="Edit"></span></a>
           <ul class="dropdown-menu">
             <li><a href="" ng-click="editSettings()"><span class="glyphicon glyphicon-cog"></span>&emsp;<span translate>Settings</span></a></li>
             <li><a href="" ng-click="idDevice()"><span class="glyphicon glyphicon-qrcode"></span>&emsp;<span translate>Show ID</span></a></li>