Contributor updated ratings
Tournesol🌻 currently keeps contributors' latest ratings up to date, by managing a contributor rating database.
The database contains entries of the form < contributor, video_1, video_2, quality_criterion, confidence, value >.
As opposed to the Tournesol main database, the contributor updated rating database can be overwritten by contributor's activities.
The values of the entries are the same as in the Tournesol main database.
In particular, for any entry, we must have video_1 < video_2 in alphabetical order of video identifiers.
The contributor updated ratings database can only be updated exactly if the Tournesol main database is.