Alter book-page and pdf solr results with more info.

Adds solr results alter logic for book pages display snippets of text, number of occurrences of the search term, page this result is on, and the title of the book instead of the page title.

Adds solr results alter logic for pdfs to display snippet of text and number of occurrences of the search term in the full text.

As per https://app.asana.com/0/14428927965996/14428927966094

Depends on https://github.com/lyrasis/repository_sites/pull/78