Split barchart module

[lukavdplas]

This tries to untangle the barchart components somewhat, by separating the logic to fetch the data from the logic to render the graph/table. E.g. TimelineComponent uses a TimelineData object that handles the data fetching.

The logic in BarchartData/HistogramData/TimelineData is mostly lifted verbatim from BarchartComponent/HistogramComponent/TimelineComponent, but I had to make some changes because the data object is not embedded in the component lifecycle in the same way.

Note for review: the whole point of this is that these modules were a tangled mess (now slightly less so), so please don't spend too much time on this. Just scan the code to see if anything stands out.