Feature Request: add a staleness check for cached container Images

Is your feature request related to a problem? Please describe.
When using run_sorter, users can combine docker/singularity_image=True with delete_container_files=False in their scripts. Assuming a users implements a "set it and forget it` approach, it is conceivable that the eventually the user will not be running on the latest version of the container for whichever package they are using.

Describe the solution you'd like
An ability to update (or auto-update) the container used, checking for if a container is old and updating if necessary. Maybe a flag like auto_update_container_image

Describe alternatives you've considered
I've considered working with IT to discuss how to manage the images and whether or not the users should be manually specifying the container images.

Start at the run_sorter entry point and trace how docker/singularity_image and delete_container_files control cached container use. Define the staleness signal, update behavior, and auto_update_container_image option; done means an old cached image can be detected and updated according to the chosen behavior.