Worked on polar charts. Connected line graphs across 0.
Some minor updates to polar charts
Added yAxis.gridLineInterpolation option with possible values "circle" or "polygon" for polar charts.
Made polar area charts null points or unconnected ends meet in center.
Implemented correct tooltip position for line type series in polar chart.
Various changes and improvements to polar charts
Merge remote-tracking branch 'origin/master' into radial

Conflicts:
	js/parts/MouseTracker.js
	js/parts/Series.js
Couple of improvements in polar charts
Fixed some issues in development of polar charts
Some more development on polar charts
Added AreaSplineRange and ColumnRange series types
Various fixes and improvements related to radial axes
Some fixes to gauges
Various fixes and improvements for radial axes, gauges and polar charts.
Added better animation to polar charts. Created general wrap utility function to wrap an object method.
Fixed missing polar columns in VML
Implemented chart click event with correct axis values in polar charts
Implemented splines for polar charts
Worked on polar charts, extending the X axis tick positions so that they auto connect across 0.
Worked around back stack drawing of areas in polar charts.