Set the originalyear tag when loading a release.

Another small and straightforward commit. Since Picard now supports both a `originaldate` and `originalyear` field it should also fill both,

In https://github.com/musicbrainz/picard/commit/388b429b0b35b9a1608156b66bb7ec3b1c8e3e51 I actually already used both tags (since ASF tags distinguish between both fields), so this commit is necessary for that to work as intented.