Consistent data output between module configurations

[nichollsh]

For the inference project (and likely for other applications), we need to make sure that the output structure of the model is consistent between module configurations.

For example: the radius of the planet is already stored in the helpfile for all possible module configurations - this is good. However, the emission spectrum is only calculated when using AGNI or JANUS. It would be valuable to have an emission spectrum when using the dummy atmosphere module. I am sure that there are other examples of missing variables under certain configurations.

@timlichtenberg