title: Persisting and accessing values globally in multiple components in Angular 2
body: <p>I have a settings page where users can save some config variables, such as a Username. The user can also change the username on that page. But when I go to another Component (page) and back, the username isn't saved.</p>
  
  <p>I also want to show the username in the other components. How do I do that? With a global variable?</p>
  
  <p>Structure: 
  - App
      - app.ts (main)
      - setting.ts
      - someOtherComponent.ts</p>