Kibana ruby auth

The existing kibana-ruby-auth ldap module only allowed authentication with a bare username.  This diff adds support for one common way that bindDNs are formulated.

Also, I added a bypass to LDAP authentication for the Auth_Admin_User.  Without this, you have to run Kibana once with auth_elasticsearch in order to set up a local account for an LDAP user, give that user admin rights, and then change to auth_ldap.