Add Polar chart support...
Add Polar chart support
This commit also heavily refactors things as polar chart needs
separate implementation of various classes that previously
only needed one, such as ChartAxis and ChartLayout.
Task-number: QTRD-1757
Change-Id: I3d3db23920314987ceef3ae92879960b833b7136
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@digia.com>