added first version of CanBusDoubleFTSensor driver

Still have to test on the real robot, given that the double ft sensor setup has not been installed on the robot.

@randaz81 everything should be ok, I still have some doubts in two points, I will comment inline in the code. 
Also in the original `CanBusAnalogSensor` we update the `status` member variable if something goes wrong, but then we don't use it in the `read()` method. Is this ok?