Adding ability to configure Traffic Manager in SetAutopilotAction (for Carla)

[t27]

Addressing #27

Adding arguments to the SetAutopilotAction to allow for setting some TrafficManager parameters for agents in a Scenic scenario. This could be extended to add more actor specific traffic manager parameters in the future as well.

Example Scenic behavior with this in practice,

# assuming all necessary imports are done before this section

VEHICLE_PERC_SPEED_DIFF = -30
SPEED_VIOLATION_PROB = 60 # probability that a vehicle is a speed limit violator(always exceeds speed limit)
TL_VIOLATION_PROB = 70  # probability with which the vehicle may violate a traffic light - this prob is constant for all vehicles

# Background activity
background_vehicles = []
for _ in range(25):
    lane = Uniform(*network.lanes)
    spot = OrientedPoint on lane.centerline
    kwargs = {"ignore_lights_percentage":TL_VIOLATION_PROB}
    if (random()*100) < SPEED_VIOLATION_PROB:
        kwargs["vehicle_percentage_speed_difference"] = VEHICLE_PERC_SPEED_DIFF
    background_car = Car at spot,
        with behavior AutopilotBehavior(**kwargs)
    background_vehicles.append(background_car)

#assuming ego vehicle is initialized after this section