Summary:
The `AffineChannel` op wrapper did not use the officially sanctioned
version of parameter creation, namely using `ModelHelper.create_param()`
Presumably this was because of the `share_with` option where you could share
parameters.

While doing this though, the parameters were never initialized! This probably
doesn't matter for the algorithm (those params get overwritten pretty quickly)
but it's a bug nevertheless. I decided to kill the `share_with` option since
this isn't used anyway and resort to the standard way of creating weights and
biases.

Reviewed By: rbgirshick

Differential Revision: D6826914

fbshipit-source-id: 65628c59b085b9ab160006b003dd40dbefa2f7c1