`AutoEncoder` does not have docstrings

[yiheng-wang-nv]

Hi @rijobro , I just found the AutoEncoder and VarAutoEncoder classes does not have docstrings, should we add? Thanks!

[rijobro]

@ericspod I ported this from ptproto, was it based on a particular implementation or should I write general docstrings?

[ericspod]

I don't have specific docstrings for these, they were meant to be basic base level implementations that use template methods to define the network structure like the way our UNet works. It would be great if you could add some basic info on the arguments and what the _get_* methods do. Thanks!