UI updates

• Add a service worker so that (mobile) browsers now automatically offer installing FacilMap as an app.

Bug fixes

• Make local storage persistent. This makes sure that the browser doesn't clear bookmarks when the system is running low in disk space.
• Fix an error where mobile phones were showing the desktop view instead of the mobile view.

Technical changes

• Use spatial indexes for line/route points and markers. This drastically reduces the loading time for maps that have a lot of routes.