Implement a widget that shows the statistics state as comboboxes
and the statistics chart. Calls into the statistics code if any
of the comboboxes changes.
The hardest part here is the formatting of the charts list with
its icons and with headings. Sadly, it is not trivial to arrange
icons horizontally. Therefore we would have to fully reimplement
the ComboBox view, which is probably not fun.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
