[TASK] Add labels to form fields of admin panel

Labels make it much easier to click check boxes and to
reach fields.

Change-Id: Ib9c42f4859a4fc4e30fc7f03dd525795d0824449
Resolves: #49073
Reviewed-on: https://review.typo3.org/21372
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer