scattergeo lat/lon OR locations

[nicolaskruchten]

Right now when you create a scattergeo trace (aka Atlas Map) you see this:

But in fact you can't use lat/lon and locations at the same time, it's one or the other. Furthermore when you give locations, the locationmode attr appears. This locationmode is also used in choropleth though.

So we need:

1. A super-widget that handles locations and locationmode together and shares visibility
2. A super-super-widget that allows users of scattergeo to say "I want to give my data in lat/lon" or "I want to give my data by location"