Add Bin Relocation FWBW example

[Leo428]

Hi guys, this PR adds the following code:

1. gym env and wrapper for franka bin relocation forward and backward task
2. add trainer support for multi learner nodes support for forward backward training
3. add recording scripts for training demos and images used for training the binary classifier (which only uses front camera images to classify)
4. add training and eval scripts for running RL with binary classifier
5. add BC training and eval scripts, as well as BC demo collection script

Thank you for the review!

[youliangtan]

Drop in some comments. otherwise gtg

[youliangtan]

is okay to hardcode for now, but at least make the path configurable as DEFINE_string() flag

[Leo428]

@youliangtan, I addressed the comments above in the new commits and replies. Thank you so much for reviewing!