Part 1: Move Conformance Section to Last-Numbered Chapter

Move Section 2 Document Processing and Conformance to the end, where it will be section 20 after sections 3 through 20 are renumbered back to 2 through 19. This will nicely restore the numbering against which previous comments on cd02 and cd03 are referenced. If a need for a Document Processing topic remains, add it to the end of the current section 3 (before renumbering) or some other non-disruptive location. (Alternatively, introduce two additional concepts, that of an implementation familiar document in which all unsupported foreign elements and attributes are (conceptually) elimiinated and a purified document in which all foreign elements and attributes and unrecognized attribute values are treated as (conceptually) not pesent. These are relevant to document validity in the presence of foreign items and to cases of document consumption and production.)