charts / heatmap: xAxis of type AxisType.DATETIME / x-Value of SeriesToolti

Hello,
i use vaadin 7.7.6 and charts 3.1.0...
I have 3 questions about the heatmap:
Is there a possibility to implement the heatmap-xAxis of type AxisType.DATETIME? (I can not get the same automated label distribution as of datetime Axis if i use the combination of HeatSeries / AxisType.CATEGORY)
How can i get the x-Value into SeriesTooltip? (this.x, series.x and point.x don't works in headerFormat-String).
If i set the title of ColorAxis (conf.getColorAxis().getTitle().setText("...")), i can't see it. Why?
Gruß
Stanislav

...working with charts 3.1.0 heatmap is really daunting...
If i set the ColorAxis.setVisible(false) i see the gray bar instead...