#742 Record dust jacket status

[Darrah Chavey]

To a book collector, it is important to know whether or not a book was released with a dust jacket or not. Although we will not always know this status, and it would be very time-consuming to go back and add this data, it would still be useful to have a field for this fact. It should have three states: Released with a dust jacket; Released with no dj; Dust Jacket status unknown. (And, of course, default to "unknown".)