Ensure zerodot redirects stay on zerodot if OK

Also, shim in the optimal language code on the
language landing page before the other languages.
The optimal language code may not even be in showLangs,
which is totally cool in the case that the operator
zero-rates all languages. This shimming concept was
okay'd by the director and product tech manager.

Change-Id: I8cc307dd2cceb604b834ee6e23107e8b9c2e951d
Merge "Ensure zerodot redirects stay on zerodot if OK"