Legend on aggregate charts is not updated on full update

[helge79]

Expected Behaviour

When using a full data update via chart.update() on an aggregate chart both chart and legend below update

Actual Behaviour

The legend is not updated. If you resize the window (or switch phone's orientation) the legend will get updated with the currently displayed values

Steps to Reproduce:

• Create an aggregate chart like "pie", "donut" or "percentage"
• Update the dataset, e.g. via button toggle

Frappé Charts version: 1.5.7 JSFiddle: https://jsfiddle.net/z2ckgrtm/

[helge79]

I added a PR. Simply updating the legend as I do solves the issue but without an animation it looks of course a bit jerky