Break out artifact generation into subcommand tree in CLI

[dotsdl]

Currently the behavior of the fah-xchem CLI is rather monolithic, with many arguments required (along with two config files) to e.g. generate-artifacts.

Although these parameters are necessary in some form, each subcommand likely requires only a subset, allowing for greater flexibility in executing workflow components from the command line. Breaking the components into their own subcommand also allows re-running only some components when troubleshooting.