Fixed miss copy code in Game object (lki, cards), removed unused code. Possible fixes:

* simulated games was able to change objects from another games (ConcurrentModificationException, related to d202278ccd, details in 3a6cdd2615);
* AI: fixed cards disappear in multiplayer games with computer (details in #6738);

Mage/src/main/java/mage/cards/MeldCard.java

@@ -36,6 +36,9 @@ public abstract class MeldCard extends CardImpl {
         this.halves = new CardsImpl(card.halves);
     }
 
+    @Override
+    public abstract MeldCard copy();
+
     public void setMelded(boolean isMelded, Game game) {
         game.getState().getCardState(getId()).setMelded(isMelded);
     }