Merge: File and Bytes

A bit of a fix in the context of issues #1267 and #1262.

The bytes module has a `ByteBuffer` class, while it is still working with `Int` at the moment, when Nit correctly supports `Bytes`, we can change it to a real `ByteBuffer`

This class is highly recommended when working with byte streams and collections.

As such, file operations are related to this module since most of the operations are working on bytes, what they mean is up to the end-user to figure.

Pull-Request: #1309
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Romain Chanoir <chanoir.romain@courrier.uqam.ca>
Reviewed-by: Ait younes Mehdi Adel <overpex@gmail.com>
Reviewed-by: Alexis Laferrière <alexis.laf@xymus.net>

diff --cc lib/standard/file.nit
Simple merge