The `clone` method now accepts any type of input but also recursively perform a deep copy of the array items. Rewrite the `configMerge` and `scaleMerge` helpers which now rely on a new generic and customizable `merge` method, that one accepts a target object in which multiple sources are deep copied. Note that the target (first argument) is not cloned and will be modified after calling `merge(target, sources)`. Add a `mergeIf` helper which merge the source properties only if they do not exist in the target object.
For consistency with `valueOrDefault`, `valueAtIndexOrDefault` now returns null if `value` (expected array) is null. Also get rid of the superfluous `get` prefix in `getValueOrDefault` and `getValueAtIndexOrDefault`.
Move some of the "core" and "canvas" utils in `helpers.core.js` and `helpers.canvas.js` and introduce the new `isNullOrUndef` and `isObject` helpers. Deprecate `indexOf` and rename `drawRoundedRectangle` to `roundedRect` which now creates a simple `rect` path if radius is 0. Write missing unit tests for the moved helpers.
The `fill` option now accepts the index of the target dataset (number) or a string starting by "+" or "-" followed by a number representing the dataset index relative to the current one (e.g. `fill: "-2"` on dataset at index 3 will fill to dataset at index 1). It's also possible to "propagate" the filling to the target of an hidden dataset (`options.plugins.filler.propagate`). Fill boundaries `zero`, `top` and `bottom` have been deprecated and replaced by `origin`, `start` and `end`.
Implementation has been moved out of the line element into a new plugin (`src/plugins/plugin.filler.js`) and does not rely anymore on the deprecated model `scaleTop`, `scaleBottom` and `scaleZero` values. Drawing Bézier splines has been refactored in the canvas helpers (note that `Chart.helpers.canvas` is now an alias of `Chart.canvasHelpers`).
Add 3 new examples and extend utils with a pseudo-random number generator that can be initialized with `srand`. That makes possible to design examples starting always with the same initial data.
