Feat/concurrent loading album

Load albums and images to display in the background to improve responsiveness in explore albums.

src/main/java/NTNU/IDATT1002/controllers/DataExchange.java

 package NTNU.IDATT1002.controllers;
 
+import NTNU.IDATT1002.database.EntityManagerConfig;
 import javafx.application.HostServices;
 
 import javax.persistence.EntityManager;
@@ -25,7 +26,7 @@ public class DataExchange {
     }
 
     public EntityManager getEntityManager() {
-        return entityManager;
+        return EntityManagerConfig.getEntityManager();
     }
 
     public HostServices getHostServices() {