add cateogory series method

...ain/java/org/knowm/xchart/demo/charts/bar/BarChart01.java

...ain/java/org/knowm/xchart/demo/charts/bar/BarChart02.java

...ain/java/org/knowm/xchart/demo/charts/bar/BarChart03.java

...ain/java/org/knowm/xchart/demo/charts/bar/BarChart04.java

...ain/java/org/knowm/xchart/demo/charts/bar/BarChart05.java

...ain/java/org/knowm/xchart/demo/charts/bar/BarChart06.java

...ain/java/org/knowm/xchart/demo/charts/bar/BarChart07.java

...ain/java/org/knowm/xchart/demo/charts/bar/BarChart08.java

...ain/java/org/knowm/xchart/demo/charts/bar/BarChart09.java

xchart/src/main/java/org/knowm/xchart/Chart.java

...c/main/java/org/knowm/xchart/internal/chartpart/Axis.java

...va/org/knowm/xchart/internal/chartpart/ChartInternal.java