Enabled --prod mode for GUI2 - refactored modules

Change-Id: I224fe9564cb225b9ebaed0a43281de54ec6eb274
diff --git a/web/gui2/src/main/webapp/app/fw/util/theme.service.ts b/web/gui2/src/main/webapp/app/fw/util/theme.service.ts
index e5c9564..fe85766 100644
--- a/web/gui2/src/main/webapp/app/fw/util/theme.service.ts
+++ b/web/gui2/src/main/webapp/app/fw/util/theme.service.ts
@@ -20,7 +20,9 @@
 /**
  * ONOS GUI -- Util -- Theme Service
  */
-@Injectable()
+@Injectable({
+  providedIn: 'root',
+})
 export class ThemeService {
     themes: string[] = ['light', 'dark'];
     thidx = 0;