Typo

Line 30 read *"men istället för HTTP används *RDF*" instead of the (presumably) intended "men istället för HTML används *RDF*".
Added links, SKOS

- Added SKOS to the first mention of RDFS and OWL for taxonomies/vocabularies/ontologies.
- Added links to the first mention of RDFS, SKOS, and OWL.
R2RML and RDF as a data model

- RDF is not a language, but a data model which can be expressed (serialised) in a variety of data languages or formats; updated a couple of paragraphs to clarify this distinction.
- Added W3C recommendation R2RML to section on converting RDF.
merging pull request by carwash