Add a simple backup option using secure copy (sftp).
Easy to use with any unix/linux target server offering ssh services. Just add a public key to `~/.ssh/authorized_keys` (`~` = users home directory), upload a matching private key and set the remote location (for example `sftp://root@192.168.1.1//root/test_backup`)
[ssh-keygen](https://man.openbsd.org/ssh-keygen.1) can be used to generate a keypair.
