Make the chart show up in the widget. This is a huge breakthrough!

We are now using KDChart version 2, and the Qt Model/View architecture. From here on, it's just a case of implementing the rest of OpenDocument and create tools for manipulating the chart.

One annoying thing: When I click in the chart area, the chart disappears. It appears as if something is covering it up. I guess I'll be able to get some help with that.