STYLE: updated documentation on selection node

Updated doxygen comments to note that the PlaceNodeClassName
calls replace the AnnotationNodeID calls. 
Fixed a merge error on the enum, fixing the overwriting of event
numbers and moved the UnitModifiedEvent to be last.
Updated doxygen comments on the annotation fiducial node to
note it as deprecated moving the top level description so that
it shows up on the generated pages.



git-svn-id: http://svn.slicer.org/Slicer4/trunk@22480 3bd1e089-480b-0410-8dfb-8563597acbee