fixed numerical axis tick label decimal formatter

...ain/java/com/xeiam/xchart/demo/charts/bar/BarChart02.java

...n/java/com/xeiam/xchart/demo/charts/date/DateChart03.java

.../com/xeiam/xchart/demo/charts/scatter/ScatterChart01.java

.../com/xeiam/xchart/demo/charts/scatter/ScatterChart04.java

...xchart/internal/chartpart/AxisTickBarChartCalculator.java

...art/internal/chartpart/AxisTickLogarithmicCalculator.java

...chart/internal/chartpart/AxisTickNumericalCalculator.java

.../com/xeiam/xchart/internal/chartpart/NumberFormatter.java

...xeiam/xchart/internal/chartpart/PlotContentLineChart.java