CI Test Suite

[Mischback]

Prerequisites

• Is the test suite working with the current, manual setup?
  • basically the test suite is working!
  • there are still some hard-coded assumptions in the test suite (mailsrv_aux.test_suite.smtp) and some configuration variables that are currently not exposed in test_runner.py; this have to be fixed!
• can a working Docker Container be created from our installation process?