Use Blacklight::AdvancedSearch from master.
Add thumbnails for Image and File collections.

Image collections get first collection member's thumb and file collections (as well as file objects) get fake cover.
Fixes invisible 'send-to' menu on smaller screens
Removes side nav's right margin in smaller screens
remove duplicate asset path
change date slider text to apply
Merge pull request #854 from sul-dlss/adv-search-facet

Use Blacklight::AdvancedSearch from master.
Add access point/masthead for Digital Collections.
Add SDR Masthead.
Merge pull request #856 from sul-dlss/collections-thumb

Add thumbnails for Image and File collections.
Merge pull request #849 from sul-dlss/coll-masthead

Add Collection and SDR Mastheads
Merge pull request #865 from sul-dlss/date-slider-button

Date slider button + sneaky commit
Merge pull request #864 from sul-dlss/send-to-menu-fix

Send to menu fix
Replaces advanced search help text