* Add index to legendItem interface for doughnut, pie and polarArea charts. Make datasetIndex optional since the before named charts dont include it.
* Remove test to check if datasetIndex has been set in generateLabels function for legend
* Relocate chart type and dataset type defaults
* Update types
* Separate overrides and descriptors
* Update derived sample, use merge for inherit
* Don't merge overrides
* Review update
* Update plugin to use it's own tooltip context
* Scriptable tooltip option types
* Tests
* Update types to use UnionToIntersection
* Update TooltipItem to use UnionToIntersection