Cleanup in response to PR comments.

Move video alpha acceptance tests into the same file as video; fix
some tests; correct non-editable metadata mutating the superclass's
data; fix typos; rename test data to make it more clear that it's just
dummy data.
Studio: revises visual layout/presentation of multi-value metadata fields
Studio: corrects minor styling/formatting for multi-value metadata fields
Fix up list view JS tests.
Disable "add setting" button if there's already a blank one.
Clean up some duplicate code.