Opacity should not be set on layer group.
Add some more helper properties for subclasses.
Enhance sn.Configuration so that when setting values (via .value()) then also create a proxy property getter/setter pair for that property.
Start work on Energy IO chart that builds on the grouped layer base chart class.
Make the bars render crisply.
Make sure getter/setter properties are deletable.
Move aggregating nest rollup function into top-level function, to share with calculating aggregate/daily values.
Work on aggregate nesting.
Work on aggregate label bands.