ORCID support: from Member API to Public API

This is a little change in the support for ORCID.
ORCID offers 2 [kinds](http://support.orcid.org/knowledgebase/articles/335483-the-public-client-orcid-api) of APIs: Member API and Public API. The first one requires a subscription with ORCID (so it is not free), while the second one is a free service limited to the OAuth login service (which is exactly what we need here).
Sorry for not having got it earlier.