fix #3484: allow setting keyboard shortcuts for specific presets and other toolbar buttons
(preset groups and custom searches are also supported), context menu item "Edit shortcut"

git-svn-id: http://josm.openstreetmap.de/svn/trunk@5954 0c6e7542-c601-0410-84e7-c038aed88b3b
Merge branch 'master' into mirror