change Collection to List

...ain/java/com/xeiam/xchart/demo/charts/bar/BarChart02.java

...n/java/com/xeiam/xchart/demo/charts/line/LineChart03.java

.../com/xeiam/xchart/demo/charts/scatter/ScatterChart01.java

...java/com/xeiam/xchart/demo/charts/theme/ThemeChart01.java

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

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

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

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

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