Support validation on multi-valued fields

[eporter23]

This ticket follows work done in #555 to validate proper ORCID entries on the creator (Authors) form entries, so that the validation occurs on any author entry and not just the first in the set.

The following fields are optional but can take multiple values. We want to enforce validation on all entries to ensure they are entered as a valid http:// or https:// URL.

• final_published_versions >> Final Published Version (URL)
• related_datasets >> Supplemental Material (URL)

[maxdmayhew]

#672