Allow specifying CLI parameters through environment variables

[danielgafni]

It may be tedious to add configuration options for all CLI parameters and flags, but it should be easy to automatically accept env vars for each parameter.

I don't know the details about the CLI implementation, but many CLI libraries allow setting something like a common env var prefix (STAX_ in this case) and then listen to env vars like PREFIX_COMMAND_SUBCOMMAND_OPTION.