STYLE: Update Models module documentation.

This patch updates the documentation file for the Display and Clipping
sections of the Models module.
Added documentation for the the View drop down and the additions to the
Scalars section.
Changed string-enumerations in Material Presets and Clipping to parameters
as they were not showing up on the wiki page.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@25018 3bd1e089-480b-0410-8dfb-8563597acbee