Files.Mod

moved NewReader/NewWriter(from prev commits) into File type and extend args for reuse instanses.
Usage:
var f1 := Files.Old(...);
var w := f1.NewReader();
var f2 := Files.Old(...);
w := f2.NewRedaer(w, 1024);
---
Reader/Wtiter -- added Base*():File; method.
Usage:
var w := Codecs.OpenOutputStream(name);
...
Files.Register(w.Base())