I should be able to easily print on cardstock forms

Summary: Consider the Item cards, or Name Badges, in ARC. (Mailing labels are another great use case.) We can currently print them by doing some delicate fiddling with CSS, but we can only print one at a time. What we should be able to do is use arbitrary Avery stock, with many cards/labels per page, making it semi-easy for the user to print onto that stock simply by designing a simple Print View and choosing some stock.

This is going to take a bunch of proof-of-concept, but seems like it should work. We need to set up the page margins carefully, then populate the page with a precisely-laid-out table, and display into boxes in that table. In principle, it seems straightforward, assuming the browser lets us have enough printer control to do it.

This should be part of a larger task, of making Printing really hum. Ideally, printing in Querki should be just as powerful and easy-to-use as in any consumer-oriented DB system.

Querki should aim to have an internal DB of all the major Avery stock eventually, although we can add that gradually. It must be possible for end users to define their own card/label stock, by setting parameters that define its margins, label size, and so on. Ideally, those parameters should be in convertible Units, so that they can be defined in either inches or cm.