tweak main search placeholder text to clarify/differentiate from single-volume search
solr page indexing to allow highlights/snippets from page text

[#67575752]
move search terms logic to search form for re-use
add single-volume search form to volume header snippet

[#67575752]
tweak main search placeholder text to clarify/differentiate from single-volume search
view and templates for searching within a single volume

[#67575752]