Center numbers in Crop and Reduce Red Eye spinboxes
When increasing the value displayed in a spinbox, normally the least
significant digit should stay in place to avoid unecessary movement.
This means the numbers should be right-aligned, instead of being
left-aligned like they are currently.
Since right-aligning still looks a bit unbalanced, centering should be a
good middle ground. In addition, when the number of digits does not
change it makes more sense to pad the number on both sides equally in
Check that the spinboxes in the Crop and Reduce Red Eye
tools look more pleasant while resizing the crop rectangle and moving
the size slider respectively. For a more profound effect, use a large
Reviewers: Gwenview, muhlenpfordt
Reviewed By: Gwenview, muhlenpfordt
Differential Revision: https://phabricator.kde.org/D14954