moved min and max to ChartInternal for better shared usage

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

...g/knowm/xchart/internal/chartpart/AxisTickCalculator.java

...t/internal/chartpart/AxisTickCategoryChartCalculator.java

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

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

...java/org/knowm/xchart/internal/chartpart/PlotContent.java

...chart/internal/chartpart/PlotContentCategoricalChart.java

.../xchart/internal/chartpart/PlotContentNumericalChart.java