Proposal: Enable setting all optional Turnkey CLI arguments using a config file

[jeremyfowers]

Description

Path to config file that enables setting all optional CLI arguments instead of explicitly setting them in the CLI.

Example:
turnkey model.py --config my_config.yaml

We may also want a corresponding command like turnkey --lots-of-args --save-config my_config.yaml, where all the args get saved to my_config.yaml.

Discussion

This issue is on hold until we identify a driving use case.

Also, we probably want a corresponding command like turnkey --lots-of-args --save-config my_config.json, where all the args get saved to my_config.json.