[Discussion] Training documentation?

Can we get some more documentation on training? There's a small [section](https://github.com/deezer/spleeter/wiki/2.-Getting-started#train-model) in the wiki, but there's no explanation of [the config file](https://github.com/deezer/spleeter/blob/master/configs/musdb_config.json). What do all the options mean (in layperson's terms, to the extent possible), and what are the ranges of acceptable values?