This was tested on ZJ-5890 with success. By default centering is
deactivated for backward compatibility. Trying to center a QR code in
native mode will raise an exception as we do not know ATM if the native
rendering is centered by default or not.
* Added basic tests for center feature
* Check image size before centering
- ported test cases for EscposImage class, copied over 1px and 2px test images from escpos-php
- added test cases over image print function
- updated QR tests to also include image output check
- updated CLI to match new image function options