Several improvements wrt URIs, SKOS-generation and mapping to other schema's

[rcdeboer]

• Creation of proper URIs (instead of URNs) that can be dereferenceable
• Promotion of Linked Data properties in ArchiMate (that start with "http" or contain a ":") to true RDF properties
• Inclusion of namespaces of a number of popular vocabularies, allowing shorthand reference in ArchiMate properties or their values
• The option to generate a SKOS enriched version of the model
• Translation of model metadata to a SKOS ConceptScheme
• The option to refer to images, generated by Archi, in SKOS output
• Translation of views to SKOS concepts
• Generation of SKOS Collections for all ArchiMate concepts in ArchiMate ontology
• Inclusion of ArchiMate definitions in ArchiMate ontology.ttl

[rcdeboer]

See (the changes in) README.md for a summary of improved and new functionality.