tools-python architecture rework

Nicolaus Weidner

Hi all,

in order to bring the Python tools up to speed and prepare them for SPDX v3, I put up a proposal for refactoring the architecture:
Happy to hear any comments about it! This will also be a topic for this and very likely the next weekly tools-python/testbed meeting (, Thursdays 5.30pm-6pm CEST / 8.30am-9am PST)

Best regards,