Show "Copy Citation" and "Copy Bibliography" when a bib format is
selected and "Copy as BibTeX", etc., when an export is selected. If a
site-specific setting is in effect from the last active URL, use that
instead.
If no regular items are selected in bib mode, the menu options are
disabled.
This also now filters non-regular items out when in bib mode -- before
if you selected a combination it would include a bunch of 'n.d.' lines.
Closes#1155, Disable Copy Citation menu option when a translator is
selected for Quick Copy
d252a09cd3