Inspired by Norm's "id.warnings" mechanisms, I
consider other stuff that we should notify/warn
users about if we find that it is missing.
For example, if there is no Refmiscinfo and
no class="source", class="manual", class="version"
found, emit a warning. Also if no Author or Editor
or Othercredit and/or not Personblurb or
Authorblurb or Contrib