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/ExploreAlbums.java

@@ -60,7 +60,7 @@ public class ExploreAlbums implements Initializable {
     public Button createAlbumButton;
 
     @FXML
-    public VBox root;
+    public VBox pageRootContainer;
     @FXML
     private HBox progressBarContainer;
     @FXML
@@ -178,7 +178,7 @@ public class ExploreAlbums implements Initializable {
      */
     private void finalizeProgress() {
         progressBar.setProgress(1);
-        root.getChildren().remove(progressBarContainer);
+        pageRootContainer.getChildren().remove(progressBarContainer);
     }
 
     /**