This commit brings a Pie Chart Widget that allows to visualize
simple information on in a single pie chart.
For now it is only used in dashboard view but it could also be
used in another view that uses a basic renderer.
An element with tat widget with attribute name 'pie_chart'
can now be added to the arch view.
Three keys should also be provided in the attribute 'attrs':
- measure (determines the field to aggregate on)
- groupby (determines the field used to group data)
- title (determines the legend of the pie chart)
Task Id: 1835644
Francois Volral
8527b01f23