Runtime limit for the code

A nice desirable feature would be to be able to specify the wall-clock time for which we want to code to run in the YAML file. When the time is up, the code dumps a restart file and exits cleanly.

One additional feature could be for the code to run a predefined bash script when exiting in this fashion. This could be used to get the job to resubmit itself and keep running. This is especially useful for long-running jobs on systems with short queues.