#25 Notification for new Updates

[Keno Albrecht]

Currently, when we publish an update for a plugin, the
user won't notice that unless She accidentaly hit the
update button in the web configuration. We should add a
feature such that the update pages for plugins are
automatically browsed. Then we could notify users
whenever a new update becomes available. This might be
a notification in the status bar of the web
configuration or even better: by adding a notification
to the Spamato toolbar in the email client or the tray bar.