icat-sync: support unsupervised registration
icat-sync-raw --register
prompt for uploading datasets that are "unregistered", "not uploaded" or "have missing files".
The first two categories require manual checking because the data might be in more than one ICAT investigation (something we should deal with at some point).
The third category however (has missing files) is safe to upload because we are sure about the selected investigation.
So we can add a flag
icat-sync-raw --auto-register
which is like --register
but then without prompting for user validation and only handling the categories that are safe to handle (only one for now: has missing files)