Switch from vostok to storagebox (fixes #51)

README.md

docs/ssh-hostkeys.txt

docs/ssh-known_hosts.txt

group_vars/all/vault_hetzner_storagebox.yml

host_vars/u236610.your-storagebox.de

host_vars/vostok.archlinux.org

hosts

playbooks/hetzner_storagebox.yml

playbooks/tasks/sync-ssh-hostkeys.yml

playbooks/vostok.yml

roles/borg-client/defaults/main.yml

roles/borg-client/templates/borg-backup.sh.j2

roles/hetzner_storagebox/tasks/main.yml

roles/hetzner_storagebox/templates/authorized_keys.j2