OAK-516 Create LdapLoginModule based on ExternalLoginModule

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1566898 13f79535-47bb-0310-9956-ffa450edef68
@trivial add explicity commons-io dependency

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1566899 13f79535-47bb-0310-9956-ffa450edef68