HIG improvements for data sampling .ui

Change-Id: I84d5f6818e1cc729b87b606de00ea342061a10a2
Reviewed-on: https://gerrit.libreoffice.org/10696
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>
Tested-by: Tomaž Vajngerl <quikee@gmail.com>