add useOnly method, set allow_extra_fields to true and filter_extra_fields to false
add useOnly method, set allow_extra_fields to true and filter_extra_fields to false

git-svn-id: f187b03b1cbfd538025a9d62a280ea5bb8acd563@16336 ee427ae8-e902-0410-961c-c3ed070cd9f9

rande/swToolboxPlugin