Add fast-loading static tile backend #25
Description
So the tileserver is slow in a way that's not scalable. It's fine for a few users but not for hundreds or more. If we do waysidemapping/beefsteak-map-tiles#11 then we can serve static tiles from a CDN and things will be nice and speedy. We'll lose the benefits of dynamic tiles, namely minutely updates, but many users won't care about that anyway. We can have static tiles be the default and then add an option to switch to dynamic tiles if desired, possibly restricted to people who log in via OSM.