fix #8500, see #8384: added "Clear buffer" button to the messages shown for incorrect buffer (clipboard)
(next Ctrl-Shift-V will paste tags from JOSM-copied objects, if available)

git-svn-id: http://josm.openstreetmap.de/svn/trunk@5809 0c6e7542-c601-0410-84e7-c038aed88b3b
fix initialization NPE (for sessions)


git-svn-id: http://josm.openstreetmap.de/svn/trunk@5810 0c6e7542-c601-0410-84e7-c038aed88b3b
mapcss: add width+height properties for repeat-image


git-svn-id: http://josm.openstreetmap.de/svn/trunk@5811 0c6e7542-c601-0410-84e7-c038aed88b3b