indexer doesn't respect @audience

[alexduryee]

The @audience attribute in EAD is used to mark elements for/not for publication. Generally, @audience="internal" marks elements that should not be published, and any other value (or no @audience at all) marks elements that should be processed normally. Arclight currently doesn't respect this element, so metadata flagged for non-publication still gets indexed and rendered.

There is a finicky case where elements with no/positive @audience attributes can have ancestors with @audience="internal":

<c @audience="internal">
  <did>
    <unittitle>Top Secret Ancestor Component</unittitle>
  </did>
  <c>
    <did>
      <unittitle>Child Component - Should This Be Indexed/Rendered?</unittitle>
    </did>
  </c>
</c>