Add custom HTTP interceptor and spinner service for request handling; update CORS settings

jambotron-ui/src/app/helpers/custom-http-interceptor.spec.ts

@@ -0,0 +1,7 @@
+import { CustomHttpInterceptor } from './custom-http-interceptor';
+
+describe('CustomHttpInterceptor', () => {
+  it('should create an instance', () => {
+    expect(new CustomHttpInterceptor()).toBeTruthy();
+  });
+});