Linked data: link out to major entities such as LoC and OCLC

[Dan Scott]

* Evergreen master

RIght now we're publishing lots of structured data--that is, schema.org classes with properties--but almost all of their values are strings. That's been a good start, but we need to connect up to the rest of the linked data cloud, and we have some very easy places to start:

1) If we have a LCCN, we can link to the corresponding Library of Congress record
2) If we have an OCLC number, we can link to the corresponding WorldCat record
3) If we have a 024 with a subfield 2 value of "uri", we can link to that universal resource identifier

These simple steps will give search engines and other aggregators crawling our data much more to work with, because they can recognize that we're describing a resource that is the same as something else that has much more linked data.

[Dan Scott (denials)]

Added http://git.evergreen-ils.org/?p=working/Evergreen.git;a=shortlog;h=refs/heads/user/dbs/lp1402921_linkout_schema_sameas - the first commit comes from bug 1402905, which should be resolved first, but the most recent commit contains the core of this actual feature.

[Dan Scott (denials)]

I'm currently rebasing this on master and adding a bit more sophistication to the branch; it's ready for testing but I'm going to remove the pullrequest tag for the moment until I've actually tested it myself.

[Dan Scott (denials)]

Okay, force-pushed a rebased version that breaks out sameAs vs. exampleOfWork links more cleanly and gave it some light testing. Adding the pullrequest tag again.

[Dan Scott (denials)]

We've been running this in production since the start of February. No ill effects reported as of yet.

[Ben Shum (bshum)]

Pushed to master for 2.8 beta. Thanks Dan!