has_provenance link from the OCC resources

[essepuntato]

Adding a direct link to the whole provenance graph (e.g. https://w3id.org/oc/corpus/ra/293031/prov/) of the resource would be valuable. For doing this, it is crucial to extend the server so as to return a view with all the statements in the provenance graph.

[Suggested by @stain as one of the reviewer of our ISWC 2017 paper]