title: Ionic: Authentication not persistent when merging to firebase v3
body: <p>I'm merging an ionic app from firebase v2 to firebase v3.</p>
  
  <p>When I use the new (v3) firebase email/password login API, I am not authenticated have to log in every time the app is re-started.</p>
  
  <p>The user should stay authenticated when first logged in into the app. Or at least this was default in the firebase v2 API.</p>
  
  <p>How can I persist the login?</p>
  
  <p>Thanks, 
  Jørgen </p>