OAK-516 - Create LdapLoginModule based on ExternalLoginModule

Fixing build failure.

Apache Felix JAAS module is currently is not avialable in Maven central. As a temporary measure commiting the LoginModuleFactory locally. Once we have a released version available this would be removed

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1567089 13f79535-47bb-0310-9956-ffa450edef68