Adopt semver for model versioning (#39)

Bumps the model version from "1.0" to "1.0.0" so future revisions can
follow semver. The model YAML and the eramba CSV artifact gain the
version in their filenames so historical versions can coexist once
additional versions are tagged.

- Rename data/pkimm-model.yaml to data/pkimm-model-1.0.0.yaml
- Set version: "1.0.0" in the model YAML and in the self-assessment data
- Constrain the schema's version field to a semver pattern
- Eramba converter now derives the input filename and the output CSV
  filename from a model_version constant, with a sanity-check against
  the YAML's version field
- Rename integrations/eramba/pkimm-v1.0.csv to pkimm-1.0.0.csv
  (regenerated CSV is byte-identical to the previous file)