Add a flag to indicate the metadata fields that can be autofilled

[matthewhorridge]

Some metadata fields can be autofilled based on the values of other fields.

Some examples:

• The SHA256 digest of a data file
• Subject Label if the Subject Identifier has been specified and the identifier is resolvable
• The creator given name, family name etc. if the creator identifier (e.g. ORCID) is specified
• The license name and license text, if the license identifier is specified
• The study name, start date, end date etc. if the PHS number is specified