In UX, back/cancel/etc buttons usually go on the left, while forward/confirm/etc go on the right. (Note that even the icon for "Back" is a leftwards-pointing arrow.) STK put the Back arrow button on general screens in the upper left corner, but before this commit, put back/cancel/etc on the right in dialogs and such. This commit fixes things to be in line with standard UX conventions, and also in line with the pre-existing upper-left corner Back button placement on screens in STK.
https://ux.stackexchange.com/a/63239
Fixes most of the occurrences of these warnings in the terminal/log:
[warn ] LayoutManager: Statically sized widgets took all the place!!
Removing these spacers did not make a difference in actual layout/spacing according to my testing.
