Since version 2.5 python-qrcode allows the direct access of the
PIL-functions. (We require version 4 and above).
Thus, we can simply call qr_img.convert() without accessing the private
member.
This refactoring is identical in functionality.
This code is adapted from the works by Frédéric Van der Essen in
pyxmlescpos.
I had to adapt the code completely in order to make it compatible with
modern unicode-handling
Further changes:
* improve text unittests in CLI and MagicEncode with hypothesis
* add feature force_encoding in order to enable old behaviour
* disable cli_text_test (for now)
* fix charcode(): it does now cooperate with the new structure
* remove redundant variable codepage from class Escpos
