Session data lost on page refresh

[Alexander-Krause-Glau]

We show the current username in the top right corner. The name is not shown on page refresh (F5 or Ctrl + R), probably due to lost session data.

This requires a fix.

We use ember-simple-auth for authentication in Ember. Issue 523 might give a hint. However, I think the problem may also origin in our session handling.

[malte-hansen]

Fixed with b4d6710