Massive kludge because self.solr_search_params_logic += [:exclude_unwanted_models] doesn't seem to be working at all
Merge branch 'develop' of https://github.com/nu-lts/drs-sufia-app into develop

Merging in upstream changes.
Small change to purge files when navigating away from the metadata step.
Refactor of GenericFile to NuCoreFile
Changing isPartOf to isMemberOf - isPartOf will be used for the forthcoming new datastream objects
Merge branch 'develop' into feature/compilations

Merging in the large refactor of the GenericFile object into a composite core type object called Nu-Core.
Adds an 'Add to Compilation' link to the actions on a file show page.