MIWP-8 (G) Conformance classes in registry

Ticket: https://ies-svn.jrc.ec.europa.eu/issues/2285

  • Make a list available on current list of Conformance classes both as URL reference and as Citations. This could e.g. be implemented through entries in the Inspire registry.
  • Unify how conformance classes should be referenced in metadata. In Data Specifications Technical Guidelines examples exist for both Citation and URL. Abstract Test Suite refers to URLs only. In TG Metadata only Citation is exemplified.