Added Polar area chart, some breaking changes.

Added Polar area chart with custom background fill.

Slight Breaking change: Changed TickInterval data type from int? to double?

Updated number types

Breaking change: From version 2.0.0 number types will no longer be of type "long". All numbers corresponding to data values will now be of type "double", and numbers corresponding to display options (ie. Height, StartAngle, BorderWidth etc.) will be of type "int"