Allow off-site reviews to be associated to IFDB members

[dfabulich]

When an IFDB member reviews a game on their own blog, any user can link to it in the off-site reviews section of IFDB.

But there's no way to say say that the review was posted by a particular IFDB user, like you can with the author of a game. Off-site reviews never appear on user profiles, because they're never associated with any particular user.

We should use the author TUID thingy on off-site reviews, as well, linking them to profiles.

[salty-horse]

More generally, off-site reviews should have an optional author field, and they don't have to be IFDB users.

In some current cases, authors are mentioned manually in the title or summary fields, which isn't ideal.