Refactoring file structure for protobufs.

Change-Id: I50daf100d54750f97158304d87813e67861b1422
diff --git a/incubator/protobuf/services/nb/src/main/proto/PlaceHolderToDelete.proto b/incubator/protobuf/services/nb/src/main/proto/PlaceHolderToDelete.proto
new file mode 100644
index 0000000..d1207dd
--- /dev/null
+++ b/incubator/protobuf/services/nb/src/main/proto/PlaceHolderToDelete.proto
@@ -0,0 +1,6 @@
+syntax="proto3";
+option java_package = "org.onosproject.grpc.net.services.nb";
+
+message ToDelete{
+
+}
\ No newline at end of file