Move digital image related code from SolrDocument to a concern, plus code refactor

Rename method to indicate behavior
Merge pull request #210 from sul-dlss/solr-document-concern

Move digital image related code from SolrDocument to a concern
Add file_id to local solr config/schema.
Remove dl/dd surrounding summary and only join it if present.
Add merged image index/show partials.
Add sort and search type configurations from old codebase.
Override blacklight paginator for local customizations.

Remove deep paging links
Change i18n value used in next/previous links to add custom character
Merge pull request #212 from sul-dlss/image-merge

Add image item merge partials
Merge pull request #213 from sul-dlss/controller-config

Add sort and search type configurations from old codebase.
Merge pull request #215 from sul-dlss/pagination

Override blacklight paginator for local customizations.
adds zero results page layout
fixes #211 by removing HOURS_API from dev.yml
adds modify your search functionality
Merge pull request #216 from sul-dlss/fix-config

fixes #211 by removing HOURS_API from dev.yml
Add helper methods for rendering MODS names...
...and use in mods upper metadata section.
Link subjects and render hierarchically.
Add helper to link URLs and email addresses from mods strings.
Merge pull request #206 from sul-dlss/zero-results

adds zero results page layout
Merge pull request #214 from sul-dlss/mods-config

Update mods parsing code in lieu of using ModsDisplay configuration.
adds merge file collection functionality

updates fixtures and only show 3 files