Total frontend revamp

[Nate-Wessel]

There area few parallel things going on here that I'll try to document because I may not have a chance to come back to this for a week or two. This is a very big, but necessary overhaul and I'm finding it hard to get it all done in one go.

• The CSS layout + div containers are dramatically simplified.
• The map component is totally gone, to be replaced by a react-leaflet implementation that should be much more declarative
• There is now a class-based data store for spatial data. It should be the ultimate source of all map state.
• All components that were tightly coupled with the previous map component need to be totally replaced. Unfortunately, that means the whole frontend...

[Nate-Wessel]

This is now about up to the level of functionality of the current deployment... which is to say there's a way to go still. But if this got merged now, no injury would be done.

[Nate-Wessel]

It has been deemed fit.