Remove references to APRS Working Group

[stevestroh]

The APRS Working Group is no longer in existence. Suggest mentioning it once as historical context (The APRS Working Group was...) and then remove further references to it. In the current era, it's irrelevant and continued references to it are just confusing; likely sending readers of this document to search for references to APRS Working Group.

Also suggest adding reference to APRS Foundation, the presumed successor organization to WB4APR's benign dictatorship, APRS Working Group, etc.... but be sure to disclaim that APRSF is not yet fully up and running to DO such work.