TrackMate_: fix annyong bug with spot visibility

Now that spot visibility is stored at the spot level and not at the
collection of spot level, we run into visbility problems when we copy
the collection. Fix this by conserving spot visibility over copy.
Most likely this bug will popup again later...
Signed-off-by: Jean-Yves Tinevez <jeanyves.tinevez@gmail.com>
MaMuT_; now use TrackMate v2.1.x

Signed-off-by: Jean-Yves Tinevez <jeanyves.tinevez@gmail.com>