#308 RenderUtilities.findLiveItems broken for NaN

[Piet]

The RenderUtilities.findLiveItems method returns faulty indices if the series contains Double.NaN as x values. In particular, datasets with DomainOrder.ASCENDING or DomainOrder.DESCDENDING do not always display all data points that are within the visible range. DomainOrder.NONE display all data points but might return a too low value for the lower bound and a too high value for the upper bound as the first Double.NaN will be interpreted as "being sinside the range".
The attached file demonstrates the issue and provides alternative implementations.