Can the registry support components without a class wrapper?

[andyk]

Reflecting on how thin the wrapper around the Gym env ended up being for the RLlib example agent...

agentos/example_agents/rllib_agent/cartpole.py

Lines 1 to 7 in 638f3ec

	# Thin wrapper around cartpole from OpenAI's Gym toolkit
	# This env models a cart with a pole balancing on top of it
	from gym.envs.classic_control.cartpole import CartPoleEnv
	class CartPole(CartPoleEnv):
	pass

...made me think that perhaps the registry could support the direct registration of a component (i.e. a class) that exists already somewhere in somebody's GitHub repo today, that is, without a wrapper like the one I wrote.

A good first candidate would be to have entries for all of the gym envs in the gym registry

[andyk]

And this would be a cool way to show off the benefits of having our programming model work directly with Python classes.