Store post view judgements

Overview

As a possible way to learn from misjudging films in advance, also store the ratings that fans gave after seeing the films.

[x] Create a Django view to review post-view ratings of films
[x] Use the films app
[x] Get access to the reviewer of a film
[x] Read the viewed films from the screening info from the C# planner
[x] Allow fans to input their post-view ratings
[x] Store the reviewer as a film attribute
[x] Create an overview of reviewers against discrepancy between pre-and post-view ratings
[x] Create a new user story as to find words or phrases that appear specifically in descriptions of misjudged films
[x] Update documentation
[x] Add tests