Allow override of private key, docker image and docker command

[tpd1001]

Allow override of private key, docker image and docker command to make script more portable.

Passing a $1 param to the script loads that private key from the ~/.ssh dir instead of the default id_rsa. The image on Docker Hub is suggested in the comment for an alternative to having built your own image. If you are using a different CRI, you should be able to override the docker command with the one you are using. Also some minor word tweaks.