Better support for resource montioring with Dstat

[aalexandrov]

This is a meta-issue for tracking the addition of Peel extensions for better resource monitoring as part of the running BDAPRO project at TU Berlin.

The work will be carried out from @Talmaj with mentoring from my side.

I suggest to add the following functionality:

• Implement a DstatEventExtractor. (added in d95ae38)
• Implement Peel commands that produce standard views over the imported resource data.