Now that the spec is finished use the unprefixed API, which was also moved
from window to navigator.
Still uses feature detection so it fail gracefully when not available in
the user agent.
AppEvents was always a service object in disguise, so we should move it
to the correct place in the application. Doing this allows other service
objects to inject it easily without container access.
In the future we should also deprecate `this.appEvents` without an
explicit injection too.
