! io, can, http: Provide information about the SSL session that an HttpMessage is received over

See https://groups.google.com/d/msg/spray-user/1r4UB3AzSeU/MHI4FL661zMJ

Some notes:
 - Session info is accessible via a new header, HttpHeaders.`SSL-Session-Info`
 - New header is added to requests on server and responses on client
 - Inclusion of header can be enabled/disabled via spray.can.parsing.ssl-session-info-header, which defaults to off
 - There's duplication between SslTlsSupport.SSLSessionEstablished and HttpHeaders.`SSL-Session-Info` but there's no common dependency between them
 - SslTlsSupport.SSLSessionEstablished.fromSession is somewhat verbose as a result of trying to avoid generation of an exception