Add multi-part viewing hint to MVW.

Closes #340

app/presenters/multi_volume_work_show_presenter.rb

@@ -2,4 +2,8 @@ class MultiVolumeWorkShowPresenter < CurationConcernsShowPresenter
   def file_presenter_class
     ::ScannedResourceShowPresenter
   end
+
+  def viewing_hint
+    'multi-part'
+  end
 end

spec/presenters/collection_show_presenter_spec.rb

@@ -37,7 +37,9 @@
   end
 
   it "can be used to create a manifest" do
-    expect { ManifestBuilder.new(subject).to_json }.not_to raise_error
+    manifest = nil
+    expect { manifest = ManifestBuilder.new(subject).to_json }.not_to raise_error
+    expect(JSON.parse(manifest)['viewingHint']).not_to eq "multi-part"
   end
 
   describe "#label" do

spec/services/manifest_builder_spec.rb

@@ -25,6 +25,7 @@
     it "renders as a collection" do
       expect(manifest['@type']).to eq "sc:Collection"
       expect(manifest['@id']).to eq "http://plum.com/concern/multi_volume_works/2/manifest"
+      expect(manifest['viewingHint']).to eq "multi-part"
     end
     it "renders a manifest for every child scanned resource" do
       expect(subject.manifests.length).to eq 1