* embed all function and new concepts into legged_robot for base implementation
* add namedarraytuple concept borrowed from astooke/rlpyt
* use namedarraytuple in rollout storage and summarize a minibatch object
* add `rollout_file` concept to store rollout data in files and demonstrations
* add state estimator module/algo implementation
* complete rewrite `play.py` example
* rename `actions_scaled_torque_clipped` to `actions_scaled_clipped`
* add example onboard codes for deploying on Go2.
Ziwen Zhuang
Fan Ziqi
Ziwen Zhuang