- 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.

- Allow setting a debug level environment variable.
- Expose port 636 (ldaps).
- Install newer version of slapd from Debian backports.
- Cleaned up the entrypoint script.