Notification

[jackd248]

Add a notification feature to get a summary of content status changes, new comments, pages which are assigned to my user, etc.
Maybe the implementation as some kind of a queue, to not get the mails immediately, e.g. triggered by scheduler task.
Also an option to cancel the notification.

[jackd248]

E-Mail notification is prepared, need some style improvements and has an issue with correct link generation from cli generated fluid mails.