Scrollable menus: update MenuScroller to last version + add mouse wheel scroll support + reset scroller when imagery menu is refreshed

git-svn-id: http://josm.openstreetmap.de/svn/trunk@5664 0c6e7542-c601-0410-84e7-c038aed88b3b
fix #8341 - Don't clear current selection in ImproveWayAccuracy mode

git-svn-id: http://josm.openstreetmap.de/svn/trunk@5665 0c6e7542-c601-0410-84e7-c038aed88b3b
Merge branch 'master' into mirror
josm-mirror: bumped externals