Accept "translator" contributors

[alainna]

Why

authors want to input the "translator" of their works in UCPMS

We've started some testing of a "translator" field in QA UCPMS in the "book" object type, example:
https://qa-oapolicy.universityofcalifornia.edu/viewobject.html?cid=1&id=4651104

What

enable "Translator" submission in manual object fields (identify the correct type so UC users will be suggested - similar to Editors)

Once "translator" can be accepted in subi, update RT2 crosswalk to accept "translator"

Bonus: let's confirm what happens when a user asserts a "is translator of" relationship of an item in Elements

[DevinSmithWork]

Coupled with eScholarship/jschol#763