Serving mode ui

@MariusVolkhart Nothing too crazy here. I added the map overlay that I showed you last week as well as an animation when you are in serving mode. I also disabled location updates while in serving mode, since we don't need them right now. We'll have to add that back when we do the automatic exit from serving mode if the vendor moves their truck.
The circle seems a bit small to me, but it's just an opinion. I kinda like it at 200dp, but your call.