Namespace URI of Domain_Fields and Ontohub metadata ontologies is “uncool”

[clange]

It is preferable to use Cool URIs to identify semantic concepts. However, our ontologies so far use rather technical URIs, which refer to a Github download location (https://raw.github.com/ontohub/OOR_Ontohub_API/master/Domain_Fields_Core.owl#). I see two problems with this:

1. A dumb linked data client should probably not be expected to know HTTPS, so we should publish these ontologies somewhere using HTTP. Oh, I see that the same URL with http would also work; it redirects :-)
2. Speaking of redirects, we should set up a more canonical URL that redirects to the actual download location of the ontology. We might want to put it into the http://purl.net/dol namespace, where I own the account. Or if “dol” is not appropriate here, let's create something like http://purl.net/oor.