PR #54: New triple term semantics in the rdf-semantics spec

I have worked on a new version of the rdf-semantics spec, including only the minimal changes necessary to extend it to triple terms, covering exactly our approved “alternative baseline” document.
Note that I had to make a minor fix to the RDF alternative semantics spec<https://github.com/w3c/rdf-star-wg/wiki/RDF-star-%22working-alternative-baseline%22>, in order to exclude that rdf:type becomes a rdf:ReificationProperty.
This version implements only a minimal change, since it could be possible also to enhance the quality of the current text.
The changes appear emphasised with a cyan background.
Discussion at the pull request "New triple term semantics in the rdf-semantics spec #54<https://github.com/w3c/rdf-semantics/pull/54>”.
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