fixes #163
Merge pull request #200 from geoblacklight/more-details-link

Add "More details at" link for those layers with a url pointer
changes some of the show page metadata
Merge pull request #203 from geoblacklight/home-metadata

changes some of the show page metadata
adds iiif image viewer
moved openseadragon to vendor/assets and formatting fixes
create submodules for dataset viewers
use rails require and leaflet classes