Develop concept for configuration

[hannobraun]

Right now, we don't have any persistent configuration. There are command-line parameters and some stuff in the UI, but no means to store configuration persistently.

Some thoughts:

• At the heart of it should be a configuration file. I prefer TOML.
• It might be useful to override configuration settings from the command line. Whether to do that manually, for selected settings, or whether there should be a CLI parameter that can systematically override any config setting, I don't know.
• Where should that configuration file live? Something in .config on Linux (and the equivalent on other platforms) might be appropriate, but maybe users would also want to override user-level configuration on a per-model basis, using a local file. For a start, it might be best to just stick with a local file and see if there's need for something more advanced.
• It would be great to be able to change settings from the GUI, but if there are multiple locations for configuration files, that poses the question how to GUI would handle that.
• Maybe there is already a crate that handles that kind of stuff.

I wanted to open this issue to write down my thoughts (because the topic came up in #37), but it's probably best to wait until we have real use cases (marking as status: blocked until then). We can collect thoughts here in the meantime.

[hannobraun]

It's not clear what needs to be done here, and there are no use cases right now, that could provide such clarity. Added to feature wishlist. Closing as not actionable.