Display correct hit count

Previously, hitCount was increased every time
a new batch of results was loaded.

src/main/webapp/app/search/search.component.ts

@@ -54,7 +54,7 @@ export class SearchComponent implements OnInit {
   }
 
   private parseSearchResultsDTO(searchResultsDTO: SearchResultsDTO): Exercise[] {
-    this.hitCount += searchResultsDTO.hitCount;
+    this.hitCount = searchResultsDTO.hitCount;
     return searchResultsDTO.searchResult.map(this.searchResultToExercise);
   }