UI enhancement: Handling of the sync notification

[ghost]

This is releated to #394

Because I'm interested in the sync progress I would like to see the progress. So mute the complete sync status is no option for me. But in my opinion, if there is no error during the sync, there is no need for a notification anymore.

So I would suggest a different handling of the sync status/progress.

I would like to see - probably animated - the overall progress (not for each account because I should know which one I asked to sync) of the sync and if there is no error I would suggest to close the notification.

So I'm able to see if everything is fine and don't need to handle the continuously upcoming notifications.

Beside that thanks for the great app 👍

[mtotschnig]

One additional point in favour of this change is that the current handling does not work if multiple accounts are synced and the information exceeds the limits of the notification.