Ability to integrate linked data authorities/subjects/genres

[dannylamb]

Transferred from Islandora/documentation#489. Please see that issue for the original conversation.

Title (Goal)	RDF UI: Ability to integrate linked data authorities/subjects/genres
Primary Actor	Repository admin, user
Scope	access
Level	Low for now, but an important requirement for the future. Potentially out of scope for RDF UI
Story	As a repository admin, I want to be able to load linked data authorities and vocabularies that can be used to autofill form fields. As a user, when I am filling out a form in Islandora with a field that uses a linked data authority, I would like to see a long select list of terms with human-readable labels that I can choose from.

[ajs6f]

It might be useful to (at least early on) make a scoping decision to support (just as an example) SKOS in particular. That would allow concrete work to go forward a bit quicker.