Implement upside-down print command

[mike42]

Example snippet:

<?php
/* Demonstration of upside-down printing */
require __DIR__ . '/vendor/autoload.php';
use Mike42\Escpos\Printer;
use Mike42\Escpos\PrintConnectors\FilePrintConnector;

$connector = new FilePrintConnector("/dev/usb/lp0");
$printer = new Printer($connector);

// Most simple example
$printer -> text("Hello\n");
$printer -> setUpsideDown(true);
$printer -> text("World\n");
$printer -> cut();
$printer -> close();

Prints:

Reference:

• Add upside-down printing  #615