ENH: Store a list of disabled plugins when user disable plugins in
advanced mode. All plugins would be enabled by default (both in simple and
advanced mode).

From: Alireza Mehrtash <mehrtash@bwh.harvard.edu>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23109 3bd1e089-480b-0410-8dfb-8563597acbee
STYLE: Added comments describing the grid transform reader behavior

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23110 3bd1e089-480b-0410-8dfb-8563597acbee