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/game/stack/Spell.java

@@ -427,7 +427,7 @@ public class Spell extends StackObjImpl implements Card {
         } else {
             idName = getId().toString().substring(0, 3);
         }
-        return getName() + " [" + idName + "]";
+        return getName() + " [" + idName + ']';
     }
 
     @Override