Improved the servers response for HEAD requests, now the server correctly
returns 405 Method Not Allowed
Fixed bug in request routing for DAP4 requests.
Fixed the JSON-LD content in the Data Request Form so that the required
description property is generated from the data set using a heuristic, or
if that fails a generic string is used. The length of this mandatory
property is now correctly limited to [50 < length < 5000]