Create a SAML2 session during login
    
    Use the updated session API to create a SAML2 session.
    Note that each session is stored discretely. Previously if
    a session for a provider already existed then that one session
    held all the session indexes. Now if a new session comes in
    it is added separately. During logout all sessions for a provider
    are retrieved and all logged-in sessions sent to the SP to
    log out.
    
    https://fedorahosted.org/ipsilon/ticket/90
    
    Signed-off-by: Rob Crittenden <rcritten@redhat.com>
    Reviewed-by: Patrick Uiterwijk <puiterwijk@redhat.com>