Added SLURM support for <cores> and <nodes> tags.
Added SLURM support for <cores> and <nodes> tags.

NOTE: SLURM does not appear to support complex task layout at job submission.
This means that complex node requests cannot be honored by Rocoto.  The SLURM 
srun comand, which users must use to actually launch parallel codes DOES support
arbitrary task layout using the -m option, and users can use that in their 
scripts to achieve whatever layout they wish.  However, Rocoto has no control 
over that and cannot enforce it.  When users specify a complex task layout 
(any <nodes> tag containing at least one '+' character), Rocoto prints a warning 
and automatically converts the request into a single 'N:ppn=M' request that will 
provide resources to satisfy the user's desired arbitrary layout which he/she
must specify with the -m option of srun..


christopherwharrop/rocoto,christopherwharrop/rocoto