[TASK] Add btn-group to ext:beuser

Resolves: #63057
Releases: master
Change-Id: Ife76126c53bc2109e5465d15ea6d2659e205ac03
Reviewed-on: http://review.typo3.org/34324
Reviewed-by: Frank Nägler <typo3@naegler.net>
Tested-by: Frank Nägler <typo3@naegler.net>
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>