Add introduction for LDAP authentication
Add introduction for LDAP authentication

apache/incubator-kylin,apache/kylin,apache/kylin,apache/incubator-kylin,apache/kylin,apache/kylin,apache/incubator-kylin,apache/incubator-kylin,apache/incubator-kylin,apache/kylin,apache/kylin,apache/kylin,apache/incubator-kylin