Publishing: Page Range Feature

Initially I designed the page-range options to be much more elaborate, offering the choice of publishing from-to certain variation codes and other almost-never-used frills.

To get this done was hard enough - there were some problems with the positioning code when publishing page ranges to HTML.

It's now time to finish the diagram-generation code, which is quite a lot of work but much of it is straightforward, as opposed to bughunting/-fixing of the 3rd party library I use for some of the publishing module.