[Meta] Thought collection of the pre V3.0.0 release review

[SchoolGuy]

This list should represent things we do want to possibly do for the next release V3.1.0:

• setup.py: long_description should be the README.md instead of a custom string
• init.py: We do want to have a main docstring for the Koan module - currently empty.
• app.py: Move CLI stuff into own module
• CLI: optparse --> argparse
• CLI: Add Version command
• License: Replace long text with SPDX text
• Obsolete scripts in bin/
• Docs: ovz-install
• Reasonable defaults instead of just none in app.py
• Check custom exceptions and maybe remove some of them
• Check and document optional dependencies
• Docs: Update and consolidate
• Code organization: Move *-create.py into submodule and shorten filenames
• Pacakging: maybe create subpackages to not install all virt types
• Check if register script is also available in Cobbler
• Check utils.py for obsolete stuff
• Tests: Raise coverage at least to 20%
• Packaging: native Debian