Patch #27: Converts Cray-specific #PBS directives in sbatch. I

            did this in preparation for the migration from PBS
            which will start next week.

sbatch: support mpp.* PBS variants

This adds support for Cray-specific PBS directives:
 * mppwidth: Task width (corresponds to --ntasks). This is not
             directly mapped, depends on the other parameters.
 * mppmem:   Memory in units of k/m/g. Default unit is Mbyte, kbyte units
             are rounded up to the next Mbyte. Actual amount depends on
	     mppnppn.
 * mppdepth: Task depth, maps into --cpus-per-task.
 * mppnppn:  Processing elements per node, maps into --ntasks-per-node.
 * mppnodes: Nodelist. In contrast to PBS, requires nid%05u prefix, i.e
             the comma-separated list contains single entries nid%05u 
	     and/or ranges nid%05u-nid%05u.