Health checks and model introspection

[BGWoodward]

It is desired to have a health check and model introspection endpoint. The rough structure would be to have a specific key in Redis that held a list of model keys and health time stamps. When getting added to the cluster, a model would add itself to that list, including relevant metadata about itself, with a health check time stamp, and periodically update it. The list of metadata and job server statuses would then be accessible for various purposes. The templates for model architectures will need to be updated to account for this