enhance chest object handling and save/load functionality

src/de/miaurizius/jgame2d/entity/obstacle/ChestObj.java

@@ -8,13 +8,10 @@ import de.miaurizius.jgame2d.entity.Entity;
 public class ChestObj extends Entity {
 
     GamePanel panel;
-    Entity loot;
-    boolean opened;
 
-    public ChestObj(GamePanel panel, Entity loot) {
+    public ChestObj(GamePanel panel) {
         super(panel);
         this.panel = panel;
-        this.loot = loot;
         type = EntityType.OBSTACLE;
         name = "chest";
 
@@ -31,11 +28,16 @@ public class ChestObj extends Entity {
         solidAreaDefaultY = solidArea.y;
     }
 
+    @Override
+    public void setLoot(Entity loot) {
+        this.loot = loot;
+    }
+
     @Override
     public void interact() {
         panel.gameState = GameState.DIALOGUE;
 
-        if(opened) {
+        if(this.opened) {
             panel.ui.currentDialogue = "It's already empty...";
             return;
         }