Improve named actor interface

actor.go

@@ -30,7 +30,7 @@ type Actor interface {
 }
 
 // Named is any object with a name.
-type Named() string {
+type Named interface {
 	// Name returns the name. This doesn't need to be the same as Type. It
 	// must return the same string every time. It is used to differentiate
 	// actors of the same type in logs.