allow configuration of axis working space to tick space ratio

xchart/src/main/java/com/xeiam/xchart/StyleManager.java

xchart/src/main/java/com/xeiam/xchart/internal/Utils.java

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

...iam/xchart/internal/chartpart/AxisTickDateCalculator.java

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

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

...ava/com/xeiam/xchart/internal/chartpart/ChartPainter.java

...c/main/java/com/xeiam/xchart/internal/chartpart/Plot.java

.../xeiam/xchart/internal/chartpart/PlotContentBarChart.java

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