Fix filling bar charts by data point

When using a HistogramRenderer with renderer.setDrawBars(true) and renderer.setPolyLineStyle(LineStyle.NONE), setting a fill colour on an individual data point per dataset.addDataStyle(index, "fillColor=cyan;") was not working.

The HistogramRenderer unit tests were already attempting to test this feature, but within the test environment the data point styles weren't being provided to the renderer correctly. This has also been addressed.

I've updated the reference screenshot accordingly, however I may need your guidance on whether that's appropriate because there are a couple of significant issues from me running on macOS:

- The fonts are rendered quite differently to the original reference snapshot
- I believe my localisation settings are causing the y-axis numbers to be formatted differently, UK style (0.50) instead of European (0,500).

I can see that FuzzyTestImageUtils.compareAndWriteReference does have some tolerance to differences, however I expect in this case I'm exceeding the threshold, in which case I might need your assistance to generate another reference snapshot which is closer and more meaningful.

chartfx-chart/src/main/java/de/gsi/chart/renderer/spi/HistogramRenderer.java

@@ -268,6 +268,7 @@ protected void drawBars(final GraphicsContext gc, final List<DataSet> dataSets,
                     gc.save();
                     DefaultRenderColorScheme.setMarkerScheme(gc, dataPointStyle, lindex);
                     DefaultRenderColorScheme.setLineScheme(gc, dataPointStyle, lindex);
+                    DefaultRenderColorScheme.setFillScheme(gc, dataPointStyle, lindex);
                     DefaultRenderColorScheme.setGraphicsContextAttributes(gc, dataPointStyle);
                 }
                 double topRadius = isRoundedCorner() ? Math.max(0, Math.min(getRoundedCornerRadius(), 0.5 * binWidth)) : 0.0;

chartfx-dataset/src/main/java/de/gsi/dataset/testdata/spi/AbstractTestFunction.java

@@ -61,11 +61,6 @@ public ErrorType getErrorType(final int dimIndex) {
         return super.getErrorType(dimIndex);
     }
 
-    @Override
-    public final String getStyle(final int index) { // NOPMD by steinhagen on 08/06/19 10:12
-        return null;
-    }
-
     @Override
     public D update() {
         lock().writeLockGuard(() -> {