Studio support for creating and editing libraries (PR 6046)

Duplicates https://github.com/edx/edx-platform/pull/6046 to allow Marco to review without spamming the reviewers on the original PR.
I thought the label on the creation field was used in the URL, which would make the Library Code and Library Identifier two names for the same thing. I'm fine with either, but we should definitely remove the Course Number label for libraries.