Requesting calendar/contacts backup

feature-request

#1

Hi there!

I just saw this https://github.com/BernieO/calcardbackup/releases and tought something similar more integrated would be nice.

The normal SQL-Backup sometimes is a mess because if I deleted just one contact then I wouldn’t want to restore the whole database just for that. But if I could click on the backup an all the contacts of the adressbook would be back to the state of the backup this would be nice.

Same thing for tasks and appointments!