First attempt to fix launchcmd for PBSPro machines

XE testing has been failing saying that aprun doesn't have enough resources.
for PBSPro this is because when you do a qsub, you have to give it the number
of nodes you want and the number of cores per node. This is what we do in the
pbs-aprun launcher. This adds code to the launchcmd script, that mirrors how we
detect the number of cpus to reserve in the pbs launcher.
Fix up initial effort of launchcmd for PBSPro

I don't know python...

Tested, and seems to be working
Remove extra newline that I inserted by accident
Minor cleanup from Thomas' review
Fix a typo
Merge pull request #244 from ronawho/fix-aprun-launcher

Fix launchcmd script to work with PBSPro 

For qsub, PBSPro requires that you reserve the number of nodes, as well as the
number of cpus per node. This adds that logic to the launchcmd script for
PBSPro (it's not needed for MOAB/TORQUE.)

This behavior matches what we do in our pbs-aprun launcher, and the method for
determining the number of cores to reserve is based off of the code in the
launcher as well.