Valkyrie Prototype: Add PCDM properties to filesets

[abelemlih]

Tasks:

• [ ] Add PCDM properties to the ValkyrieFileSet model
• [ ] When user clicks "Create FileSets from Attached Files", add PCDM object properties to Fedora 6 metadata for that particular fileset
• [ ] Ensure "Create FileSets from Attached Files" is idempotent
• [ ] Ensure PCDM hasMember is empty when "Remove FileSets Created from Attached Files" is clicked (at the work level)

[abelemlih]

@eporter23 for this ticket we will need to test the following:

When the button "Create FileSets from Attached Files" is clicked:

• Each fileset has the property rdf_type set to http://pcdm.org/models#Object
• Each fileset has the property memberOf set to the ID of the parent work
• The parent work has property hasMember set to the list of fileset IDs that belong to that work
• The button action is idempotent

When the button "Remove FileSets Created from Attached Files" is clicked:

• The parent work has property hasMember set to an empty array
• The button action is idempotent

[eporter23]

@abelemlih looks good! One thing I want to note is that in Hyrax-created objects, FileSets don't usually have memberOf (parent work) stored. I don't know if there is a reason for that, and it seems like a good thing to have, but wanted to mention it. Example from Fedora 4/Hyrax FileSet: http://fedora-cor-test.library.emory.edu/fcrepo/rest/prod/58/70/vt/4b/5870vt4bkn-cor