[WIP] Stop duplicate names

[paddyroddy]

I'm running into issues with the "Default" name. I think we need two tests:

• test_load_config which would load a valid config name, i.e. not one of cell or particle
• test_load_config_duplicate_config which would raise an error when attempting to load an existing config name, i.e. cell or particle

I haven't got this working, and we've run out of time