Read base URI from actual model (Core profile) + add owl:versionInfo

[bact]

Use the Core namespace in the model as source, instead of hard-coded in parser.

To resolve #203

Note that the base IRI is updated to the MAJOR-only one: https://spdx.org/rdf/3/terms/

owl:versionIRI can be generated, if a version metadata is provided, like this:

## Metadata

- id: https://spdx.org/rdf/3/terms/Core
- name: Core
- version: 3.1

From this example,

• Base IRI (in owl:Ontology) will be https://spdx.org/rdf/3/terms/
• owl:versionInfo will be 3.1
• owl:versionIRI will be https://spdx.org/rdf/3.1/terms/

If version is absent from namespace metadata, owl:versionInfo and owl:versionIRI are omitted silently. The ontology remains valid OWL.