Implemented previously unsupported parameters.

module/VuFind/src/VuFind/Search/Summon/Results.php

@@ -350,8 +350,16 @@ class Results extends \VuFind\Search\Base\Results
             $limit = 50;
         }
         $params->resetFacetConfig();
+        if (null !== $facetSort && 'count' !== $facetSort) {
+            throw new \Exception("$facetSort facet sort not supported by Summon.");
+        }
         foreach ($facetfields as $facet) {
             $params->addFacet($facet . ',or,' . $page . ',' . $limit);
+
+            // Clear existing filters for the selected field if necessary:
+            if ($removeFilter) {
+                $params->removeAllFilters($facet);
+            }
         }
         $params = $params->getBackendParameters();
         $collection = $this->getSearchService()->search(