Add current time to stationboard response

[chdh]

Please add the current time to the JSON response structure of the stationboard request. That way we would have a more reliable time base than using the local client time for computing time differences to future departures.

While the server already sends a "Date" field within the HTTP response header, it seems not to be possible to the get that with JQuery (jqXHR.getAllResponseHeaders() does not contain the "Date" header).