see #8652 (patch by cmuelle8, part 1, modified): add "toggle panels" action (soon will be on Tab)
rework all toolbar context menus (add "do not hide" item and remove PopupMenuLauncher usage)
fixing minor warnings (@Override, private final)

git-svn-id: http://josm.openstreetmap.de/svn/trunk@5965 0c6e7542-c601-0410-84e7-c038aed88b3b