title: angular2firebase - multiple instances using Angular 6
body: <p>I'm upgrading to <code>Angular 6</code> using <code>AngularFire2</code>. My app referenced 2 <code>Firebase</code> projects using code like this to create the database reference:</p>
  
  <pre><code>public initFirebaseApp(config: FirebaseAppConfig, firebaseAppName: string) {
          this._db = new AngularFireDatabase(_firebaseAppFactory(config, firebaseAppName));
      }
  </code></pre>
  
  <p>This code is now broken. I get this: </p>
  
  <pre><code>ERROR in src/app/services/firebase.service.ts(24,25): error TS2554: Expected 5 arguments, but got 1.
  </code></pre>
  
  <p>Thanks!</p>