v0.1.0-rc11 Improve Clean task initial condition and Goal height

Task: Cleaning Table

Primitives

1. place A into box, both on table.
2. place B into box, with A already inside the box.

Training Mixture: 1 + 2, 50:50.

Test: Both A and B on table, and place both into the box. (edited)

Name	Observation Spec	Goal Init/Comment
Clean-i-v0	achieved_goal: (6,) desired_goal: (6,) observation: (43,)	place the first object into the box
Clean-ii-v0	achieved_goal: (6,) desired_goal: (6,) observation: (43,)	place the second object into the box while the first one is already in there.
Clean-train-v0	achieved_goal: (6,) desired_goal: (6,) observation: (43,)	50/50 mixture of both
Clean-v0	achieved_goal: (6,) desired_goal: (6,) observation: (43,)	Start with both on the table, place both into the box.

twin_box_envs = [
    'fetch:Clean-i-v0',
    'fetch:Clean-ii-v0',
    'fetch:Clean-train-v0',
    'fetch:Clean-v0',
    'fetch:Clean-aside-i-v0',
    'fetch:Clean-aside-ii-v0',
    'fetch:Clean-aside-train-v0',
    'fetch:Clean-aside-v0',
]

Clean-i-v0	distribution
Clean-ii-v0	distribution
Clean-train-v0	distribution
Clean-v0	distribution
Clean-aside-i-v0	distribution
Clean-aside-ii-v0	distribution
Clean-aside-train-v0	distribution
Clean-aside-v0	distribution