Bars and unified hover location with half-years periods

[nicolaskruchten]

This pen has oddly-positioned hovers: https://codepen.io/nicolaskruchten/pen/RwVZgBW?editors=0010

[nicolaskruchten]

Also in-scope for this issue IMO is the scatter+bar case: https://codepen.io/nicolaskruchten/pen/JjNypvM