STYLE: reduce levels of parameters

Rewrite the Markups documentation file to reduce the level
of nesting in the parameters. The wiki templates only show
3 levels, so go to a flatter description so all parameters
can be displayed on the wiki.



git-svn-id: http://svn.slicer.org/Slicer4/trunk@22358 3bd1e089-480b-0410-8dfb-8563597acbee