[DEPRECATE] Placment of order attribute for cardsort problems

[Rob Beezer]

As described in a recent message here, "matching" problems began as a 1-1
correspondence. That was relaxed to allow for multiple #premise (the
draggable) to be associated with a single #response (the drop zone), and
perhaps this is when more distractors became possible. This now requires an
adjustment in how you specify a static version for outputs such as PDF and EPUB.

Formerly, the presentation of the #premise (draggable) could be given a
permuted order with an @order attribute on the containing #match. This
should now be placed on *each* #premise inside the #match (presumably with
different integer values). #response will be presented in the authored order
(as before).

If your problem is a 1-1 correspondence from before then we will honor the old
placement on #match, so no rush to change. But you will get warnings until you
edit your source. A more relaxed version of these problems needs to have proper
placment of @order or results will be unpredictable.

(Work on completely relaxed matching problems continues and will not necessitate
any more deprecations. Stay tuned.)