Implement v2 of the DFC ontologies

We are currently formulating v2.0.0 of the DFC Ontology & Taxonomies. Details of the anticipated changes can be seen in our task board.

This major release will contain breaking changes, primarily to do with naming:

• Rename Enterprise to Organization
• Move to w3id.org redirects

For those which impact the data directly we'll store some redundancy to support both versions of the ontology:

• Change handling of currencies (import QUDT's cur reference vocabulary)

Currently we're mapping the Django model and fields that to the correct classes/properties from the ontology. We'll need to expand that to support multiple mappings, and then importing data through any channel should be flexible to the data received. That should mean that we don't need to negotiate the version during import and can just be tolerant of the data received.

On the proxy side we'll be able to output data in the v2, always - and thus treat these properties as the "preferred" format, as opposed to implementing a content negotiation around the version of models and fields used.