Actually the hardware barcode implementation is very specific and not
generic enough for just adding a `soft_render=True` argument to it. This
is a first work that can be improved with other commits, maybe for
merging this method in the `barcode` method after some cleanup.
The width, height and text_distance were set using empiric
print-and-retry tests so that the generated barcode looks nice to the
eye (and to the eye of an Android scanner tool.
!WARNING! Printing a barcode that is too large in width will result in
the printer to go crazy trying to print an image that is too large for
it. This may be fixed by raising an exception in the `image` method.
Romain Porte