STYLE: DataProbe: Refactor adding functions to generate text descriptions

This commits adds the functions to facilitate the customization
of the text displayed in the data probe in extension.

Function added are:

• generateViewDescription(self, xyz, ras, sliceNode, sliceLogic)
• generateLayerName(self, slicerLayerLogic)
• generateIJKPixelDescription(self, ijk, slicerLayerLogic)
• generateIJKPixelValueDescription(self, ijk, slicerLayerLogic)

Co-authored-by: Davide Punzo <punzodavide@hotmail.it>

From: Jean-Christophe Fillion-Robin <jchris.fillionr@kitware.com>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@24552 3bd1e089-480b-0410-8dfb-8563597acbee