Remove custom environments which duplicate openai/gym

[ryanjulian]

Inventory of custom environments

Category	Name (<>Env)	openai/gym?	Meta- dep?	Notes
Box2D	CarParking	No	No
Box2D	Cartpole	Yes	No
Box2D	CartpoleSwingUp	No	No	Pendulum-v0 is a radial joint rather than a cart-pole
Box2D	DoublePendulum	Yes	No	Acrobot-v1
Box2D	MountainCar	Yes	No
MuJoCo	Ant	Yes	Yes
MuJoCo	HalfCheetah	Yes	Yes
MuJoCo	Hopper	Yes	Yes
MuJoCo	Humanoid	Yes	No
MuJoCo	InvertedDoublePendulum	Yes	No
MuJoCo	Point	No	Yes
MuJoCo	SimpleHumanoid	No	No
MuJoCo	Swimmer3D	No	Yes	Not clear this one is working
MuJoCo	Swimmer	Yes	Yes	Not clear this one is working
MuJoCo	Walker2D	Yes	Yes
Meta-MuJoCo	AntGather	No	-
Meta-MuJoCo	PointGather	No	-
Meta-MuJoCo	SwimmerGather	No	-
Meta-MuJoCo	AntHill	No	-
Meta-MuJoCo	HalfCheetahHill	No	-
Meta-MuJoCo	HopperHill	No	-
Meta-MuJoCo	Swimmer3DHill	No	-
Meta-MuJoCo	Walker2DHill	No	-
Meta-MuJoCo	AntMaze	No	-
Meta-MuJoCo	PointMaze	No	-
Meta-MuJoCo	SwimmerMaze	No	-

[ryanjulian]

Based on above, the first candidates for deletion are:

• Box2D/Cartpole
• Box2D/DoublePendulum
• Box2D/MountainCar
• MuJoCo/Humanoid
• MuJoCo/InvertedDoublePendulum

[jaekyeom]

@ryanjulian I think it would be nice to mention that many of the custom environments have been moved to https://github.com/rlworkgroup/metaworlds somewhere.

[ryanjulian]

@jaekyeom I'd be happy to review a pull request for this!