Add role prefix to role specifig variable to avoid conflicts when
using multiples role on the same machine on the same play.

Role to configure nextcloud with LDAP User backend.

First test passed.

New modules:

- occ:
  set coniguration values using `php occ` nextcloud command-line tool.

- Tasks splitted in subfiles.
- Static slapd configuration (slapd.conf) moved *properly* to dynamic
conf (slapd.d).
- TLS Enabled by default, with certificate acquired using
  `ca_manager`.
- New default tree
- New default ACL
- Kerberos schema added
- {SSHA512} hash properly configured.