numbers in scarpet better handle long type values.

If possible, numbers that can be represented as longs (seeds, etc) will be handled as longs but they will loose their longinness with a single arithmetic operation.

src/main/java/carpet/script/value/FunctionValue.java

@@ -120,7 +120,7 @@ public class FunctionValue extends Value implements Fluff.ILazyFunction
     }
 
     @Override
-    public double readNumber()
+    public double readDoubleNumber()
     {
         throw new InternalExpressionException("Function value has no numeric value");
     }