GitLab

QtCharts can't deal with charts being deleted, so we need to update them
rather than to re-create them.

The singular chart now also shows correct values.

This avoids having to special-case it all over the place.

We now have a dedicated class per aggregation handling model setup and
chart creation.

This fixes dangling line series crashing when the model they still listen
to resets.

This is now superseded by more fine-grained control about data and
aggregation types.

Also, add three different view modes, for analytics, surveys and schema
editing.