Refactoring Keyword mapping, introducing tuples

Src/AST/Myc.Ast.RTL.Core.pas

@@ -540,7 +540,7 @@ begin
     if Args[1].Kind <> vkMethod then
         raise EArgumentException.Create('The second argument to Map must be a function.');
 
-    Result := TDataValue.FromSeries(TDataValue.Map(sourceArg.AsSeries, Args[1].AsMethod()));
+    Result := TDataValue.Map(sourceArg.AsSeries, Args[1].AsMethod());
 end;
 
 class function TRtlFunctions.Reduce(const Args: TArray<TDataValue>): TDataValue;
@@ -629,8 +629,7 @@ begin
             Result := TDataValue(sourceSeries.Items[idx]);
         end;
 
-    finalSeries := TDataValue.Map(indexSeries, mapperFunc);
-    Result := TDataValue.FromSeries(finalSeries);
+    Result := TDataValue.Map(indexSeries, mapperFunc);
 end;
 
 class function TRtlFunctions.Any(const Args: TArray<TDataValue>): TDataValue;