Merge: Delete serialisations and link to prov store documents

As agreed at #84 with @nicholsn, @nicholst and @satra, this pull request:
- Remove the `ttl`, `json`, `png`, `svg`, `pdf` serialisations from the repository.
- For each example (examples/spm; examples/spm/example001; examples/fsl...) include a README file pointing to the corresponding document in the prov store and `json`, `ttl` and `svg` serialisations.

This will, in particular, ease the review of new pull requests and potentially avoid unnecessary rebasing.