Added HTTPS param with Apache-like behaviour to fastcgi/scgi/uwsgi_params (fixes #38).

conf/fastcgi_params

@@ -9,6 +9,7 @@ fastcgi_param  REQUEST_URI        $request_uri;
 fastcgi_param  DOCUMENT_URI       $document_uri;
 fastcgi_param  DOCUMENT_ROOT      $document_root;
 fastcgi_param  SERVER_PROTOCOL    $server_protocol;
+fastcgi_param  HTTPS              $https if_not_empty;
 
 fastcgi_param  GATEWAY_INTERFACE  CGI/1.1;
 fastcgi_param  SERVER_SOFTWARE    nginx/$nginx_version;