Make Statistics Panel update when an ROI is selected for the Area Probe Graphs

[ameraner]

Note: ported from EUM Gitlab issue 186

This feature request proposes to update the Statistics Panel when an ROI is selected to create an Area Probe Graph. The Statistics values should be recomputed using the pixels contained inside the region.

Comment by Alexander:

What do you think about that the statistics panel could stay as is but an additional statistics table could be added to the Area Probe Graphs pane?

This would have the internal technical advantage, that the current way the full-data statistics are calculated, stored and updated could stay as is, but it may also be an interesting option for the end user to be able to see both.

It has also disadvantages though: the displayed statistics would not follow a selection change in the Layer Manager, but would be linked to the layer(s) selected in the according Area Probe Graph tab.

Comment by Dave:

I'm not a scientist, but I like the idea of being able to compare statistics between different regions (by switching tabs)...if that is possible.