Serials: When the fully compressed serial holdings are active in the OPAC,

Serials: When the fully compressed serial holdings are active in the OPAC,
you get this "issues held" display with an expand/compress toggle that will
either show you individual holdings (and allow you to place holds on them)
or compressed holdings statements.

The functionality existed in trunk before this commit, but this cleans it up
and makes it better. It's more consistent with the the result detail table,
it doesn't offer you the change to place holds on issues that don't have
units (copy-equivalent objects), etc etc.

git-svn-id: svn://svn.open-ils.org/ILS/trunk@18931 dcc99617-32d9-48b4-a31d-7c20da2025e4