charts 8.x-3.0-alpha9

This release includes:

Module dependency to the chart plugin's module not added in the view config
Undefined offset error when using pie and donut charts with C3
Dependency Injection for Charts style plugin
Chart Attachments no longer inherit their parent contextual or exposed filters
Undefined index exporting in Drupal\charts_highcharts\Plugin\chart\Highcharts->buildVariables line 205
Highcharts pie/donut charts should be able to accommodate one node (or an aggregation) with multiple fields

As well as changes to code formatting and some work on the template_preprocess_views_view_charts(), which makes it much easier to follow.