document use of ORCID ids in userId field

[mbjones]

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Author Name: Matt Jones (Matt Jones)
Original Redmine Issue: 6574, https://projects.ecoinformatics.org/ecoinfo/issues/6574
Original Date: 2014-07-03
Original Assignee: Matt Jones

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Kyle Braak [GBIF] has requested that we document how to use ORCID ids in EML documentation. He writes:

Just a thought, but to promote ORCIDs a bit, how about adding http://orcid.org/ to the list of examples in the "directory" documentation: https://knb.ecoinformatics.org/#external//emlparser/docs/eml-2.1.1/./eml-party.html#directory? Another candidate could be Researcher IDs (e.g. http://www.researcherid.com/rid/C-4862-2011).

This includes describing the use of the http://orcid.org site as the directory, and showing an example of an ORCID in the text. We should also mak eit clear that a userId from a public source like ORCID is much more useful than a local userid from a site-specific system.

[mbjones]

Added userid documentation in the 2.2 branch, merged from @amoeba . This is closed and ready for review.