Move adding camera, controller, drivetrain into functions

[Ezward]

This is the first step in updating the path_follow.py template to use GPS. This step is just to make the same sensor available in complete.py available to any template, and to simplify the complete.py template as well. The full process for merging in the GPS branch can be found in [Issue 991}(https://github.com//issues/991#issuecomment-1242763724)

• refactored complete.py to move adding of common parts into functions that can be shared with other templates (path follow in particular).
  • add_drivetrain() adds the configured drive train to the vehicle.
  • add_odometry() adds configured encoders to the vehicle.
  • get_camera()/add_camera() adds configured camera(s) to the vehicle.
  • add_simulator() adds donkey gym if it is configured.
  • add_user_controller() adds the webui and any configured game controller, or the donkey hat.

[DocGarbanzo]

Looks good to me. It's probably hard to test, because you can have all possible combinations of controllers, drive-trains, cameras, etc. Did you test some of the common combinations?

[Ezward]

I am going to run this branch this weekend at the diyrobocars race and if all goes well I will merge. Thank you for the approval @DocGarbanzo