[bug 1068720] Forums per language per product

I still need an admin interface for this, but does this look okay? I had a way more complicated way I was trying to do this and then figured this was probably the best solution. 3 commits for 3 stages of migrations.

f?
This relies on the stuff in settings.py, right? Eventually I bet we will want to remove that information from settings.py, and then this migration would break. In the interest of keeping migrations self contained, maybe it would be better to copy the list of supported locales into this file and reference it locally?