Improve gello pip packaging

[etaoxing]

Improve pip packaging of gello/ code for pip install git+https://github.com/wuphilipp/gello_software.git.

[etaoxing]

@AndreasJosefGassner @wuphilipp

any chance of merging these changes so pip install "gello @ https://github.com/wuphilipp/gello_software.git" is more usable?

currently installs like:

gello/
  __init__.py
  dynamixel/
    __init__.py
    driver.py
  env.py

these changes should add all the source files:

gello/
  __init__.py
  agents/
  cameras/
  data_utils/
  dm_control_tasks/
  dynamixel/
  env.py
  factr/
  robots/
  utils/
  zmq_core/