Added enumeration axis option to spider chart.

...k/src/org/fortiss/tooling/spiderchart/example/Sample.java

...k/src/org/fortiss/tooling/spiderchart/model/AxisBase.java

...src/org/fortiss/tooling/spiderchart/model/DataSeries.java

...src/org/fortiss/tooling/spiderchart/model/DoubleAxis.java

...rg/fortiss/tooling/spiderchart/model/EnumerationAxis.java

...rc/org/fortiss/tooling/spiderchart/model/SpiderChart.java

.../src/org/fortiss/tooling/spiderchart/style/AxisStyle.java

...src/org/fortiss/tooling/spiderchart/style/ChartStyle.java

...rg/fortiss/tooling/spiderchart/style/DataSeriesStyle.java

...k/src/org/fortiss/tooling/spiderchart/util/AxisUtils.java

...fortiss/tooling/spiderchart/widget/SpiderChartWidget.java