adds the possibility to define border styles for each data point from the series. works for bar, line, area, scatter, pie

[kotlyarevskyy]

Adds a new 'styles' property to the OptsChartData interface to define styles for data points.
Adds logic that allows custom border styles to be defined for each data point in the following charts: Bar, Line, Area, Scatter, Pie/Doughnut charts.

the data array would look like this, e.g:

data: [
    {
	 name: 'Project Status',
	labels: ['Red', 'On Hold', 'Green', 'Unknown'],
	values: [10, 20, 38, 2]
	styles: [
		{border: {pt: 2, color: '#ff0000'}} // RED BORDER FOR THE FIRST DATA POINT
		{}
		{border: {pt: 2, color: '#00ff00'}} // GREEN BORDER FOR THE THIRD DATA POINT
		{}
	 ]
    }
]