Theme hard-codes assumption that the backing ILS is Evergreen

[gmcharlt]

Commit 31a81c4 directly refers to data structures that are provided only by the Evergreen ILS driver to display the circulating library name and any monograph parts associated with an item. As a consequence, the theme will not correct display holdings from (say) Koha.

At minimum, the Evergreen-specific behavior should be behind an check of the active ILS driver(s). Better yet would be teaching the ILS driver to include parts when it provides call numbers to the theme.