Use the configured unique key field instead of hard-coding 'id'
Few more minor places where we reference a document's unique key as 'id'.
Merge pull request #780 from sul-dlss/more-ids

Few more minor places where we reference a document's unique key as 'id'
Merge pull request #770 from sul-dlss/unique-key

Use the configured unique key field instead of hard-coding 'id'