Add container_cmd_args option for single containers

[cfelder]

• container_run_args provide all flags for podman-run(1)
• container_cmd_args can be used complementary for providing a cmd and it's args after specifying the image

e.g. podman run --name certbot --rm -v ... docker.io/certbot/certbot \ certonly --webroot --webroot-path=/usr/share/nginx/html \ -d exmaple.com

Fixes: #6

[ikke-t]

excellent, I also learned a new use case, thanks :)

[cfelder]

Unfortunately this will need a follow up if container_cmd_args is not defined.