unify reading and writing from/to recources

[michaellilltokiwa]

The same mechanism should be used for reading/writing from/to all kinds of resources. (files, network connection, pipes, stdout/stdin, etc.)

It should be possible to do this buffered and unbuffered.

[maxteufel]

this is, essentially, what i'm trying to do currently. there is no nice way for unbuffered reading/writing, but this should be as easy as duplicating the buffered reader/writer effects but without handling buffering. they can both use the io.Read/Write_Provider