improve citation of archival materials in bibliographies

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See ​forum discussion and ​Simon's post on xbiblio list. For Chicago, from Simon's email:

"If only one item from an archive:
Do not include locator information (box, etc.) in citation(?),
instead specifying it in the bibliography
Include item information in bibliography

If more than one item from the same archive:
Include locator information in citation
Include only one bibliography entry and exclude item-specific variables"

Australian National Archive requires a different style (see forum discussion above).

Depends on #210.