Removed helpers to get associated documents.
Created related_objects partial is each repository model controller to display related objects.
Removed generic related_object partial from application views.
Added i18n for is_external_target_for association.
Added find_parent method to HasParentBehavior controller concern to permit the `parent' method to work for all views.
Fixes #1206
Merge pull request #1208 from duke-libraries/hotfix-1206

Removed helpers to get associated documents.