Improvements to SETTINGS

[thequilo]

The current SETTINGS might need some improvements. The main point is that the SETTINGS are not checked, so you can set invalid settings without noticing it. Most annoyingly, if you make a typo, e.g., SETTINGS.CONFIG.READ_ONY_CONFIG=False, it has no effect at all although you think you set it correctly.

Possible improvements:

• Block setting non-existent keys
• Check set values before accessing them
• Add the ability to set them globally (e.g., environment variables, ~/.sacredrc or something)
• Add CLI option for settings (not possible for all settings as some settings have an effect on the command line parsing or are used before the command line arguments are parsed)