[BUGFIX] Improve checkboxes in user settings

Change-Id: Ifb72a8cb8236a370dab9c6d8604adf7ba02fc06d
Resolves: #63125
Releases: master
Reviewed-on: http://review.typo3.org/34437
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>