Add new measurement backend based on powerjoular project

Since it is not clear that Scaphandre continues to be maintained, we should explore other backends. One option that appears to be well documented is Powerjoular: https://github.com/joular/powerjoular. 

Our approach will be to create a separate container image for powerjoular and start it in a separate process, passing the PID it should monitor as part of the container command line arg. 