WIP: Logistration Third Party Auth Fixes

@dianakhuang @rlucioni This is a stab at updating the logistration form to include the fixes for third party auth in the current release candidate.

There are a lot of commits here because of the merge from the RC (which we should do anyway).  The important commit is: https://github.com/edx/edx-platform/commit/c553a47c262853f45c50051dd6053e156ae109cc

I'm not going to have a chance to fully test and merge this before I leave for California, but hopefully this provides a good starting point.