Verify SSL certificate

[ConsoleCriminal]

Right now, checking of the SSL certificate of the LDAP server is hardcoded disabled:

ldap.set_option(ldap.OPT_X_TLS_REQUIRE_CERT, ldap.OPT_X_TLS_NEVER)

This barely adds much security at all, except for the connection itself being encrypted. Consider adding an option whether to check or not.