listImpl should return the file names and not their paths

I don't know why I was sure it had to return the paths of the files. I've now read the documentation again and looks like it has to return only the file names.
There's a todo here because for directories listImpl should return the name + "/", but I haven't implemented this yet (it requires some more work, I'll file an issue).
This could be simply `var fileArray = new Int8Array(bytesFile)`, but perhaps it's better not to bypass *ctx.newPrimitiveArray*.

(We could also add an *initialValue* parameter to *newPrimitiveArray*.)