Debian package improvements

Description

Improvements in the Debian package originally from #46 (closed).

Tasks

• Consider to offer the Debian package also through https://deb.torproject.org.
• Debian bug #989926: purging fails when removing users.
• Add the Debian package test procedure into the [development procedure](docs/development.md], perhaps generalized for the Debian package, the Python package and also for testing directly from source code. Perhaps this procedure could be integrated into a multi-step shell script.
• Debian package should ship executables on /usr/bin not /usr/sbin.
• Remove data folder away from the configurator module?