Allow override configuration with command line args [enhancement]

[tijsmaas]

Nice work to streamline config files! What I usually do is load the configuration file, but allow the command line arguments to override the settings. The advantage is that the conf file does not need changing for every small experiment.

The hierarchy stays the same, for example in the (yaml) conf file:

sound:
    volume_left: 50

Could be exec'd with modified settings like so:
myfile.py --sound.volume_left 80

If you like the idea, I can implement the feature.