Improve HIG for Calc Descriptive Statistics .ui

Descriptive statistics

Change-Id: I8d3377e9c814f674bee4c09b562a02e80e7ed000
Reviewed-on: https://gerrit.libreoffice.org/10691
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>
Tested-by: Tomaž Vajngerl <quikee@gmail.com>