Wikidata: Add property IDs (#215)
Wikidata: Add property IDs (#215)

* Wikidata: Add back Property IDs

Property IDs are the real fields; the labels are just that, labels that 
can change and are available in different languages. On top of that, the 
properties cannot be accessed by label other than via search.

Reverts part of e45d66e

* Wikidata: Add mappings

codemeta/codemeta,codemeta/codemeta