Map improvements

Yet another batch of fixes.
This makes the map much more useful:
- speedup is configurable (both as query parameter and interactively on the page)
- real time tracking works correctly, even when the car stops
- updates can be stopped

There is a TON more work to be done here. The problem is that I'm learning as I'm doing this so I keep finding stuff that is broken and need to keep going back to fix things everywhere. Hopefully I'll have some more time tonight to get this all to a clean state...