GitLab

For now, this is a basic one intended just to run the common role on
every host.

This way we can separate informations into different files so that it's
easier to read.

This new role contains for now only a task related to the
authorized_keys file to manage SSH keys.

Add ansible.cfg file

See merge request !1

* set the default hosts file
* disable retry files by default
* always show the diff

Also edited README to remove -i