All 1-character strings converted to primitives

"b" + "r" now changed to 'b' + 'w'.  It's more straight-forward, and may cause perfomance improvements - character primitives allocation is faster and less expensive than string creation.

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

@@ -206,7 +206,7 @@ public class CardsImpl extends LinkedHashSet<UUID> implements Cards, Serializabl
         }
         Collections.sort(cards);
         for (String name : cards) {
-            sb.append(name).append(":");
+            sb.append(name).append(':');
         }
         return sb.toString();
     }