it's a love-hate relationship...
added a new class inside canvasPane, vertRect, in which we store
everything associated with a particular vertical bar in the chart, as
follows: the rectangle object, the country, the first attribute name,
the second attribute name, the first attribute value and the second
attribute value
this way it will be really easy to show this information in the info
panel and also much easier to detect what rectangle we are when we click
on it