app/views/catalog/_physical_holding.xml.builder: throws enumerative code into a partial. Also breaks out items into their own element with associative barcode, vol/issue, and status.
app/views/catalog/_supplemental_link.xml.builder: a partial created for the requested supplemental links addition.
app/views/catalog/show.xml.builder:
Adds the holding type boolean elements.
Points to the partial above for the supplemental links.
Partializes the holdings elements and also renames them since we are now referring to online resources.
spec/system/view_show_page_spec.rb: Updates the spec to expect the new elements and structure.