Add top app bar for easier navigation within the app

[rexhansen]

When navigating deep into the app, it may require many actions to get back to the home page, which can be quite cumbersome (eg try doing 10 searches back to back, view a map, then get back to the home page). To resolve this issue in other apps (Store, Bing News, etc) a top app bar is available to go back to the home page (as well as other locations in the app).