WIP refactor instances to handle digital objects
WIP backend changes for instances linked to DOs
WIP add missing files
WIP working on getting singular relationships working
WIP fix
Complete backend work to support digital object links on instances + tests
Add frontend readonly view for instance digital object link
Enhance subrecord_form partial to allow custom action - used to implement typed template insertion for instances
Fix extra fields <div> around container form and remove debug puts
Allow filtering of values from factory#sample
Remove trailing whitespace
Merge pull request #241 from hudmol/instance-digital-object-links

[Delivers #41509633] Instance digital object links