By Tom Bemis Self-driving vehicle service backed by GM wins approval from California to begin offering rides. The idea of self-driving vehicles that carry people to and from wherever they want to go has been a hot one in Silicon Valley for a long time. The dream has been to eliminate the need for drivers by using a combination of cameras, sensors and computing power to run cars on city streets. That could provide all kinds of benefits from convenience, to freeing up time otherwise spent driving, to improved driving and passenger safety. The battle to develop the technology and make it practica…