RobotEmitterReceiver class should inherit from Webots Robot class

[tsampazk]

RobotEmitterReceiver class should inherit from Webots Robot class if possible, similarly to other deepbots classes which inherit from Webots Supervisor class, so that it can access whatever Webots method directly.

Right now it needs this:

        self.robot = Robot()

and then accesses internal methods as self.robot.getBasicTimeStep() or self.robot.step(self.timestep).

Inheriting the Robot class will make this class more consistent with other deepbots classes.