enhance chest object handling and save/load functionality

src/de/miaurizius/jgame2d/data/DataStorage.java

@@ -23,6 +23,14 @@ public class DataStorage implements Serializable {
     // PLAYER INVENTORY
     List<String> itemNames = new ArrayList<>();
     List<Integer> itemAmounts = new ArrayList<>();
+    int currentWeaponSlot;
+    int currentShieldSlot;
 
+    // MAP OBJECTS
+    String[][] mapObjectNames;
+    int[][] mapObjectWorldX;
+    int[][] mapObjectWorldY;
+    String[][] mapObjectLootNames;
+    boolean[][] mapObjectOpened;
 
 }