[TASK] Twitter Bootstrap EXT:beuser follow up

* Visual streamlining of EXT:beuser
* align buttons in button groups and fillup empty buttons.
* hide the "hide" button for current loggedin user

Resolves: #63075
Relates: #63057
Releases: master
Change-Id: I1b0313de0ab086d7a1facb6fa2456ce502ba8fc4
Reviewed-on: http://review.typo3.org/34348
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>
Reviewed-by: Frank Nägler <typo3@naegler.net>
Tested-by: Frank Nägler <typo3@naegler.net>