Improved filtering tracks by date: more convenient (see #8416)
allow sorting track table, ignore broken timestamps for filtering and colorizing
DateEditorWithSlider widget can be reused

git-svn-id: http://josm.openstreetmap.de/svn/trunk@5815 0c6e7542-c601-0410-84e7-c038aed88b3b
Merge branch 'master' into mirror