Feature request: Option to select four images to be shown at once instead of two.

[QuentinWach]

TrueSkill scales to multiple images, so we can show multiple images and speed up the ranking that way.
Add the ability to switch between two and four images dynamically (during ranking) using a settings button on the left.
Note that the progress bar should be updated accordingly.
Show four instead of two buttons below in this case which can be pressed manually or using the 1,2,3,4 keys.