improve update script, so it can be used without modification

git-svn-id: http://svn.openstreetmap.org/applications/utils/tirex@29791 b9d5c4c9-76e1-0310-9c85-f3177eceb1e4
disable by default as was before

git-svn-id: http://svn.openstreetmap.org/applications/utils/tirex@29792 b9d5c4c9-76e1-0310-9c85-f3177eceb1e4