add filter option, in order to show only signs with tag info


git-svn-id: http://svn.openstreetmap.org/applications/editors/josm/plugins@29230 b9d5c4c9-76e1-0310-9c85-f3177eceb1e4
make window size & layout persistent


git-svn-id: http://svn.openstreetmap.org/applications/editors/josm/plugins@29232 b9d5c4c9-76e1-0310-9c85-f3177eceb1e4