qualified names are working

I did change things a bit, simplifying them for citation processing.

Given {x/y}, x must be a data set and y must be in x. Further, x must be referencable from the current context.

One advantage here is that you can identify a page in a particular data set. With the more powerful notations, this kind of qualification was not working.

And that's it for the weekend. References are out of wack at this point, as well as citation processing. They're next.