* tagchecker: ignore keys starting with `source:`
* utils: handle unicode character '\uFEFF' (ZERO WIDTH NO-BREAK SPACE)

git-svn-id: http://josm.openstreetmap.de/svn/trunk@6410 0c6e7542-c601-0410-84e7-c038aed88b3b
Merge branch 'master' into mirror