- hadolint and docker-compose config.
- Fix what hadolint complained about.

- Use a patch to change the configuration files (instead of fiddling
with sed).
- Don't log the healthcheck requests.

- ldap-account-manager is not available on Debian buster right now, use
Debian sid instead.
- Document the default password.

- Replaced phpLDAPadmin with ldap-account-manager as the webui.
- Added nss-pam-ldapd as a test client.