* fixed crash before proper error message for invalid choice of non-string
objects.
* fixed: Paths can be handled by `save_options_to_config` (converted to strings)
* fixed: Quotes around Paths are stripped from config files on reading
* fixes: Strings with linebreaks are now written properly with `save_options_to_config`
* fixed `None` write and read in config files.
* added tests for list-lengths of default parameters.
* improved `create_parameter_help` function.
* some documentation fixed/additions.
* switched to github actions for CI.