GUI -- Added distinct icon for nav-menu in the masthead.

Change-Id: If0ceed757cf580c80159e67af7f1b03671c78147
diff --git a/web/gui/src/main/webapp/app/fw/mast/mast.html b/web/gui/src/main/webapp/app/fw/mast/mast.html
index 216b01c..a5ddbc6 100644
--- a/web/gui/src/main/webapp/app/fw/mast/mast.html
+++ b/web/gui/src/main/webapp/app/fw/mast/mast.html
@@ -1,4 +1,6 @@
 <!-- Masthead partial HTML -->
-<img class="logo" src="data/img/onos-logo.png" ng-click="mastCtrl.toggleNav()">
+<img class="nav-menu-button" src="data/img/nav-menu.png"
+     ng-click="mastCtrl.toggleNav()"></div>
+<img class="logo" src="data/img/onos-logo.png">
 <span class="title">Open Network Operating System</span>
 <div id="mast-right"></div>