Set processing elems per node when using PBSPro launcher.

This is how we feel about it: http://goo.gl/B6gcYe
Merge pull request #497 from thomasvandoren/fix-launchcmd-for-pbsproc

Set processing elems per node when using PBSPro launcher.

This is how we feel about it: http://goo.gl/B6gcYe