Modify power save mode so that nodes can be powered off when idle. See

    https://computing.llnl.gov/linux/slurm/power_save.html or 
    "man slurm.conf" (SuspendProgram and related parameters) for more 
    information.
This is the final installment of the work: update some documenation, 
    increase default ResumeRate, and reduce frequency of retrying 
    batch launch state check.