further work on real-time charts

...in/java/com/xeiam/xchart/standalone/RealtimeAttempt1.java

...in/java/com/xeiam/xchart/standalone/RealtimeAttempt3.java

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

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

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

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

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

...xchart/internal/chartpart/AxisTickBarChartCalculator.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

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