Fixes for some common errors

Thanks to the introduction of HockeyApp in the last version, I was able to locate some of the main reasons for failing.
I cannot guarantee that these are already solved. For some, it will be a better handling of the error, for others it might be that the location is more clear after this update.

On the PokehashKey page, there is also a button in the top right corner to 'forget' the current Access token, so when you press 'Store and continue', the app will go to the Login page, without automatic login.