Be able to provide a NameIDFormat to LogoutRequest

[pitbulk]

Be able to provide a NameIDFormat to LogoutRequest, not only NameiD value

We can't assume that the NameID format stored on the settings is the same that the one the IdP uses.
Example: set unespecified on settings and get an EmailAddress format.

We should be able also to retrieve from an auth object the NameID format., right now only retrieves
the value. SAMLResponse getNameIdData method contains the format info.