Various stuff:
 * see #9414: remove old DeprecatedTags test
 * refactor some classes in `gui.preferences` package
 * improve javadoc

git-svn-id: http://josm.openstreetmap.de/svn/trunk@6529 0c6e7542-c601-0410-84e7-c038aed88b3b
Merge branch 'master' into mirror