Adding skeletal structure for the ONLP gNMI GUI demo.

Change-Id: I6796ebf200e20a51bdc098fcc3696b78d7c1132e
diff --git a/apps/onlp-demo/src/main/resources/app/view/odTopov/odTopov.css b/apps/onlp-demo/src/main/resources/app/view/odTopov/odTopov.css
new file mode 100644
index 0000000..8aa18f6
--- /dev/null
+++ b/apps/onlp-demo/src/main/resources/app/view/odTopov/odTopov.css
@@ -0,0 +1,2 @@
+/* css for layout topology overlay  */
+