figshare API #4

the figshare API may offer a way to access open licensed figure metadata and the actual files.

Docs are here: https://github.com/figshare/user_documentation/blob/master/APIv2/index.md

The public API endpoints do not include item file data, but the private ones do - hopefully private here just means needing to authenticate, rather than only being able to see one's own data.

Steps:

1. search for images with open licenses https://github.com/figshare/user_documentation/blob/master/APIv2/articles.md#search-public-articles
2. get the metadata record for each article, e.g. https://api.figshare.com/v2/articles/2064108
3. take the id of each article and use the article files private API to list files and get their URLs: https://github.com/figshare/user_documentation/blob/master/APIv2/articles.md#article-files-subsection