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 adds support for non-scalar entry properties such as size.

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

This happens for example when deleting the current product.

This propagates schema changes to the other views correctly.

This fixes losing the selection on product updates.