dspace.cfg: Enable OpenSearch

Signed-off-by: Alan Orth <alan.orth@gmail.com>
dspace.cfg: Update OpenSearch config for XMLUI

Signed-off-by: Alan Orth <alan.orth@gmail.com>
dspace.cfg: Update OpenSearch instance name

Signed-off-by: Alan Orth <alan.orth@gmail.com>
discovery.xml: Add sidebarFacet for CRP Subject

Signed-off-by: Alan Orth <alan.orth@gmail.com>