Added docstrings to main autograd functions and generated functions.
Added docstrings to main autograd functions and generated functions.

kcarnold/autograd,melgor/autograd,t1m0thy/autograd,FighterLYL/autograd,hips/autograd,hips/autograd,jackkamm/autograd,HIPS/autograd,barak/autograd,HIPS/autograd