Charging

Three small changes:
- don't drop charge state when not charging - this actually has higher resolution data on the range than the streaming data which I am planning to use in the graphs. Given the amount of data we are storing when the car is driving, one more data set per minute won't really make a differenve
- when streaming.js is started retrieve and store the vehicle state as well. Not much of this is useful in a database (who cares if the door was open), but among other things this gives us the firmware string (which might be interesting for other purposes, e.g., when dealing with sleep state
- completely unrelated, but a result of my conversations with Arthur: keep the map centered on the car