Log communications volume

[lars-t-hansen]

The context is NAICNO/Jobanalyzer#6. For multi-node jobs we want analysis to be able to flag poor use of communication. The complexity of this task - which I suspect is considerable - can be pushed into the analysis code but sonar would need to capture data about communication performed by each job on each node: volume and conduit / interface. It's OK if these data are cumulative or since-last-probe, so long as we know which.

(This is not yet high priority.)