Fix AppVeyor CI configuration

[Boddlnagg]

The current configuration in @vosen's AppVeyor is not compatible with #234. Unfortunately, the configuration is made in the UI and is not available as YAML. I have been able to work around the issue for the Release build, but fixing the Debug build definitely requires updating the AppVeyor settings, because I've removed the Debug-CI project configuration. In case you (@vosen) read this, please export your settings as YAML, so we can fix it and include it in the repository ...