support for querystring logout like Feide.no uses and some fixes

 fix ISO date issue - would sometimes emit invalid dates, use toISOString() to avoid problems like this

add includeIdentifierFormatInRequests option to not supply identifierFormat to SAML server, because ADFS really hates this for some reason, but it's important to configure the identifierFormat for ADFS signout
add logging option to write requests/responses to console
add support for querystring logout response message, since that's how feide.no does it.  can't verify the signatures from feide.no for some reason, though.
refactor logout support so we can use two response urls, one for authenticate responses and one for logout responses