Reorganize configuration

[johnerikhalse]

The configuration files contains commented code as examples of alternative configurations. This code suffers from not being updated when code changes. In addition it makes the important parts of the configuration harder to read for a newcomer.

The suggestion is to let the main configuration file contain only elements relevant for all configurations and move all the others to separate files which can be imported. No configuration needs to be commented out and it might be possible to write tests to make sure configurations are still valid after changes to codebase.