Re: [tei-council] att.global.source

In both the prose (1.3.1.1.4 "Sources, certainty, and responsibility") and the tagdoc discussing the new att.global.source, URIs are divided into "full", "fragmentary", and "private-URI syntax". I'm not sure what these mean. I would prefer we divide the world of our URIs up into "absolute", "relative", and something like "private URI that will be expanded to an absolute URI as documented in a <preFixDef> in the TEI header".

Changes and example seem reasonable to me.