Revise where to add Loading so it is clearer

This is just to list please where we could make clear that the app is doing something:

• When loging in: the loading is shown at the bottom because the app is loading which tabs to show, maybe there could be a loading icon at the center
• When loging in when using SSO browser: there is a moment that you see a blank screen 
• When loging out: for some moments you see a blank screen

Thanks!