added ability to format x and y axis independently

...-demo/src/main/java/com/xeiam/xchart/demo/XChartDemo.java

...n/java/com/xeiam/xchart/demo/charts/area/AreaChart01.java

...n/java/com/xeiam/xchart/demo/charts/area/AreaChart02.java

...va/com/xeiam/xchart/demo/charts/area/AreaLineChart03.java

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

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

...in/java/com/xeiam/xchart/internal/chartpart/AxisPair.java

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

...a/com/xeiam/xchart/internal/chartpart/AxisTickLabels.java

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

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

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