Usually the handlers appended are accessed via `handlerAt(int)` method from its subclass, but yeah, I agree that it will be more useful when it is allowed to specify the names for the specified handlers.  Let me try to fix this one.

It's useful when you have to keep some common information between handlers.  For example, `HttpClientCodec` keeps common fields shared by the encoder and the decoder.  Other `*Codec` classes don't take advantage of this feature, but it's still useful in that it helps a user add the pre-defined set of handlers to set up the pipeline easily.