Added support for multiple cars in sim

[hmcty]

Changes

• Modified sim and viz to allow for any number of cars
• Condensed ground truth and realistic viz into a single window
• Refactored launch files to allow for easy creation of new cars
• Changed variable and function names to conform to rktl standard style

Testing

You can launch the official launch file rocket_league.launch.

Then add the car in sim (kind of like setting a new car on the field):

rosservice /sim_create_car "name: 'car1'
init_pos:
  x: 0.0
  y: 0.0
  z: 0.0
init_yaw: 0.0
reset_to_random_pose: true"

Then add the car to the network:

roslaunch rktl_launch car.launch car_id:=1

To see the new car in the visualizer:

rosservice /visualizer_refresh "{}"

Future work for sim & viz + misc. updates

As of now, cars are launched with an agent type of either none, planner or autonomy. But I was thinking we could change that to control_type, then easily launch xbox and keyboard interfaces in the same launch file. With the options being: none, bezier_agent, autonomy_agent, xbox, or keyboard.

I started exploring a few different domain adaptation and randomization methods. Which could help detect issues in planners early and improve the usefulness of autonomy agents. So hopefully I can propagate some of those changes into the sim soon.

Going to push another PR today or tomorrow with additional bezier planner changes.

[dgerblick]

Made redundant by #146