[bgmxyetr] Bus with next bus display

Put on the outside curb side of the bus a live-updating display of times of the next buses arriving at the stop.  This is probably only useful for bus stops that have multiple bus routes that stop at it.

Ideally, such a display would instead be built into the bus stop itself (seen in San Francisco), but this has challenges of power, vandalism, and theft.  Initial deployment and subsequent maintenance requires an engineer to travel out to the field, instead of doing all work at the bus barn.  There are also probably more stops than buses.

On the other side of the bus, a similar display but giving the next buses for the stop across the street.  A passenger waiting at a stop across the street sees a bus stop there and can read when a bus is coming to his or her stop.

A similar display on the back of the bus for when the next bus of the same route is expected to arrive at the station just passed; for those situations of just missing a bus, seeing its back as it drives away.