Several new features in pipeline runner

* Signal treatment (pipeline can be brought down with CTRL-C)

* Ability to use cgroups resource constraining (useful to simulate GRID
  environment)

* Monitor CPU and MEMORY per task

* Ability to monitor produced/open files

* A mechanism where tasks can be (speculatively) back-filled with higher
  nice value

* psutil is now a required module

Author: sawenzel