If your dataproducer can generate more than one type of
graph and you want tooltops and links to be generated
it was impossible since ChartMapType used the type of
the provider to determine which method was caused. So
if you implemented both XYToolTipGenerator and
CategoryToolTipGenerator; the category method would be
called regardless of dataset type.
I've modified ChartMapTag to look at the class of the
dataset and make use of this information to determine
what action to take for both tooltip and link generation.