New backup role

There is a new backup role in the roles folder:

    roles/ipabackup

This role allows to backup an IPA server, to copy a backup from the
server to the controller, to copy all backups from the server to the
controller, to remove a backup from the server, to remove all backups
from the server, to restore an IPA server locally and from the controller
and also to copy a backup from the controller to the server.

Here is the documentation for the role:

    roles/ipabackup/README.md

New example playbooks have been added:

    playbooks/backup-server.yml
    playbooks/backup-server-to-controller.yml
    playbooks/copy-backup-from-server.yml
    playbooks/copy-all-backups-from-server.yml
    playbooks/remove-backup-from-server.yml
    playbooks/remove-all-backups-from-server.yml
    playbooks/copy-backup-to-server.yml
    playbooks/restore-server-from-controller.yml
    playbooks/restore-server.yml