save_results creates multiple files

[mnblonsky]

When save_results is set explicitly, there may be some strange behavior where equipment-specific and model-specific files get saved separately, rather than combined with the main output file. Not sure yet if it makes sense to change the code for this, but we should at least add a note in the docs about it. This could be an issue for other input arguments too, e.g., save_status, name (for Equipment, not Dwelling), schedule, required_inputs, optional_inputs.