another big rearrange

...n/java/com/xeiam/xchart/demo/charts/line/LineChart04.java

...n/java/com/xeiam/xchart/demo/charts/line/LineChart09.java

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

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

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

...iam/xchart/internal/chartpart/gridstep/DateFormatter.java

...eiam/xchart/internal/chartpart/gridstep/DateGridStep.java

.../xchart/internal/chartpart/gridstep/DecimalFormatter.java

...m/xchart/internal/chartpart/gridstep/DecimalGridStep.java

...om/xeiam/xchart/internal/chartpart/gridstep/GridStep.java

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

.../test/java/com/xeiam/xchart/unit/DecimalGridStepTest.java

...c/test/java/com/xeiam/xchart/unit/ValueFormatterTest.java