INSPIRE GML: documented dataset feed related parameters

Change-Id: Ib94af78fb3f9e8c8c853711690288af8329a8cb8
Reviewed-on: http://gerrit.esdi-community.eu/3184
Tested-by: Jenkins <sitemple@igd.fraunhofer.de>
Reviewed-by: Simon Templer <simon.templer@igd.fraunhofer.de>