Adding support for user interface extensions.

Change-Id: I1e41d16efc11be31ad4c2fb0c09e86e3dfd26706
diff --git a/web/gui/src/main/resources/WEB-INF/classes/css.html b/web/gui/src/main/resources/WEB-INF/classes/css.html
new file mode 100644
index 0000000..daf58b6
--- /dev/null
+++ b/web/gui/src/main/resources/WEB-INF/classes/css.html
@@ -0,0 +1,3 @@
+<link rel="stylesheet" href="app/view/sample/sample.css">
+<link rel="stylesheet" href="app/view/topo/topo.css">
+<link rel="stylesheet" href="app/view/device/device.css">