Alternate flows for: 1a. Patron browses audio books in SimplyE

Acceptance Criteria for alternate flow in step 1:

When audiobooks is turned OFF by the admin (SIMPLY-1271)

• Given a library has turned off 'audiobooks' in the circulation manager
• When they view the main catalog page
• Then they will NOT see a facet/header/selection menu 

Acceptance Criteria for alternate flow in step 3:

When audiobooks is turned ON by the admin, but no books are found.

• Given a library has turned on 'audiobooks' in the circulation manager, but no audiobooks are available in the collection
• When a patron selects 'Audiobooks'
• Then they will see a "No books available" message.

Leonard has provided the code for the entry points, and I'm pasting it below: 
 
OPDS feed with two entry points:
 
  <link simplified:facetGroupType="http://librarysimplified.org/terms/rel/entrypoint" opds:facetGroup="Formats" title="eBooks" href="https://circulation.librarysimplified.org/NYNYPL/groups/?entrypoint=Book" rel="http://opds-spec.org/facet" opds:activeFacet="true"/>
  <link simplified:facetGroupType="http://librarysimplified.org/terms/rel/entrypoint" href="https://circulation.librarysimplified.org/NYNYPL/groups/?entrypoint=Audio" opds:facetGroup="Formats" rel="http://opds-spec.org/facet" title="Audiobooks"/>
 
In this case, SimplyE should show UI for switching between entry points.
 
OPDS feed with two entry points:
 
  <link simplified:facetGroupType="http://librarysimplified.org/terms/rel/entrypoint" opds:facetGroup="Formats" title="eBooks" href="https://circulation.librarysimplified.org/NYNYPL/groups/?entrypoint=Book" rel="http://opds-spec.org/facet" opds:activeFacet="true"/>
 
In this case, SimplyE should not show a UI for switching or give any indication as to which is the current entry point.