Allow rating of films released for previews.

As an example this Danish film tt10747310 that I saw for over a week ago in a public preview, I can not rate, because the general release date is a week from now.

Actually these rating are interesting for people to decide whether they want to go and see it when generally released.

I'm talking public previews, not something with special access for a closed group.

I saw another preview Tuesday, and is to see yet another preview tonight....
And just rated a film tt10945328 that I saw at a preview a fortnight ago...
It is a bit annoying to remember to come back and rate the films when they are finally released...
(The actually rating is kept with my tiny Danish reviews at FilmR.net , but still annoying)