Typo and links

- Introduktion line 30 read \*"men istället för HTTP används *RDF*" instead of the (presumably) intended "men istället för HTML används *RDF*".
- 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.
- 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.