Add more fields to resources.

This is only a proposal and is totally open to debate.
We should be at least three to agree on something before merging.

Possible improvements:
* Extend this to any node type and not just resources. (Would it make sense?)
* Make the `image` attributes of buttons optional. (Not sure this would give a good rendering on most UIs)

Motivations:
* This basically extends what the WebUI does for Wikipedia entries to any source of data (eg. would be useful to the OEIS module)
* This would move the Wikipedia request from the WebUI to the Wikidata module (instant loading instead of ~0.5s)
We may need more data about the image (size, url of the image description/copyright...)