MAR-129: Fixed deprecation of check_invalid_arguments in m_ldap_entry:

- Updated the module itself.
- Updated the ldap_server tasks.

MAR-125: Eliminated a couple of warnings:

- Use the file module when cleaning-up the /etc/duply/main/gnupg directory.
- Mark the bind_password in m_ldap_entry and m_ldap_permissions as no_log
parameters.

MAR-117: Renamed ldap_entry and ldap_permissions modules:

- Renamed ldap_entry module to m_ldap_entry.
- Renamed ldap_permissions module to m_ldap_permissions.
- Renames done to avoid collisions with official modules (at least for
ldap_entry).