Make installation of Pygments (and Python) more robust

[tig]

Describe the bug
winprint's pretty-print functionality (within the AnsiCte content type engine) utilizes Pygments (https://pygments.org/). The pygmentize.exe executable must be available and Python 3.7, 3.8, or 3.9 must be installed (other versions may work too).

The winprint installer currently installs pygmentize.exe in \Program Files\Kindel Systems\winprint which means pygments doesn't need installation, but if Python isn't installed or configured right pretty-print won't work.

There are lots of options for fixing:

• Don't depend on pygments/python
• Version check python in installer and install proper python version if needed
• ...

[tig]

GUI now (PR #36) has a check with message box.

Still need to implement in console version and installer.