Bug 1033549: [CostControl] Add a per-app data usage list

https://bugzilla.mozilla.org/show_bug.cgi?id=1033549
I don't understand how is this working. `adaptData()` converts samples format returned by statistics API into other compatible with the render. Consider two apps A and B consuming 20MiB and 30MiB for the same date T. If you simple concatenates samples for both apps, you will end with a duplicated entry for date T. I glimpsed you perform some kind of data normalization in the render part but this seems ugly to me. I would prefer to normalize here, in the model, and provide the render with a canonical set of samples.

What do you think?