ssn action-250 and specgen labels

In the voting meeting for ssn several broken links in the ssn WD were attributed to the automated specgen processing of ssn terms without labels, and I took an action to fix ssn accordingly.

I have just done that here https://github.com/w3c/sdw/pull/507  and I will close the action. I also made the existing rdfs:label s more consistent throughout.

However, there was only one term without a label:  ie ssn:observedBy . So all  those other  broken links  had a different origin, still unknown to me.

Kerry